$NTRS
NORTHERN TRUST CORP Stock $ntrs

$ntrs Overview Financials Valuation SEC Filings Company Website

2018 Q4 Form 10-K Financial Statement

#000007312420000101 Filed on February 25, 2020

Income Statement

Concept	2018 Q4	2017 Q4	2017
Revenue	$1.662B	$1.491B	$5.375B
YoY Change	11.46%	17.97%	8.33%
Cost Of Revenue	$157.9M	$66.40M	$203.4M
YoY Change	137.8%	196.43%	124.01%
Gross Profit	$1.504B	$1.425B	$5.375B
YoY Change	5.57%	14.75%	8.33%
Gross Profit Margin	90.5%	95.55%	100.0%
Selling, General & Admin	$767.1M	$753.0M	$2.864B
YoY Change	1.87%	13.78%	9.9%
% of Gross Profit	51.01%	52.86%	53.28%
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$114.0M	$110.5M	$421.7M
YoY Change	3.17%	14.39%	12.97%
% of Gross Profit	7.58%	7.76%	7.85%
Operating Expenses	$1.018B	$973.7M	$3.698B
YoY Change	4.54%	14.3%	7.34%
Operating Profit	$485.9M	$450.8M	$1.678B
YoY Change	7.79%	15.74%	10.59%
Interest Expense			$340.2M
YoY Change			86.92%
% of Operating Profit			20.28%
Other Income/Expense, Net
YoY Change
Pretax Income	$485.9M	$435.6M	$1.634B
YoY Change	11.55%	11.84%	7.7%
Income Tax	$91.10M	$132.1M	$434.9M
% Of Pretax Income	18.75%	30.33%	26.62%
Net Earnings	$409.9M	$356.6M	$1.199B
YoY Change	14.95%	33.81%	16.13%
Net Earnings / Revenue	24.67%	23.92%	22.31%
Basic Earnings Per Share			$4.95
Diluted Earnings Per Share	$1.851M	$1.564M	$4.92
COMMON SHARES
Basic Shares Outstanding			228.3M shares
Diluted Shares Outstanding			229.7M shares

Balance Sheet

Concept	2018 Q4	2017 Q4	2017
SHORT-TERM ASSETS
Cash & Short-Term Investments	$55.82B	$51.31B	$4.518B
YoY Change	8.8%	2.96%	-15.27%
Cash & Equivalents	$4.582B	$4.518B
Short-Term Investments	$51.24B	$46.79B
Other Short-Term Assets
YoY Change
Inventory
Prepaid Expenses
Receivables
Other Receivables
Total Short-Term Assets	$4.582B	$4.518B	$4.518B
YoY Change	1.42%	-15.27%	-15.27%
LONG-TERM ASSETS
Property, Plant & Equipment	$428.2M	$464.6M	$465.0M
YoY Change	-7.83%	-0.43%	-0.43%
Goodwill	$669.3M	$605.6M
YoY Change	10.52%	16.6%
Intangibles
YoY Change
Long-Term Investments	$86.75B	$94.21B	$94.21B
YoY Change	-7.91%	20.86%	20.86%
Other Assets
YoY Change
Total Long-Term Assets	$127.6B	$134.1B	$134.1B
YoY Change	-4.8%	13.05%	13.05%
TOTAL ASSETS
Total Short-Term Assets	$4.582B	$4.518B	$4.518B
Total Long-Term Assets	$127.6B	$134.1B	$134.1B
Total Assets	$132.2B	$138.6B	$138.6B
YoY Change	-4.6%	11.83%	11.83%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses
YoY Change
Deferred Revenue
YoY Change
Short-Term Debt	$107.3B	$115.5B	$115.5B
YoY Change	-7.14%	12.88%	12.88%
Long-Term Debt Due	$7.902B	$6.051B	$6.051B
YoY Change	30.59%	18.41%	18.41%
Total Short-Term Liabilities	$115.2B	$121.6B	$121.6B
YoY Change	-5.27%	13.14%	13.14%
LONG-TERM LIABILITIES
Long-Term Debt	$3.401B	$3.224B	$3.224B
YoY Change	5.49%	3.83%	3.83%
Other Long-Term Liabilities	$3.142B	$3.588B	$3.588B
YoY Change	-12.43%	-0.66%	-0.66%
Total Long-Term Liabilities	$6.543B	$6.812B	$6.812B
YoY Change	-3.95%	1.41%	1.41%
TOTAL LIABILITIES
Total Short-Term Liabilities	$115.2B	$121.6B	$121.6B
Total Long-Term Liabilities	$6.543B	$6.812B	$6.812B
Total Liabilities	$121.7B	$128.4B	$128.4B
YoY Change	-5.2%	12.45%	12.45%
SHAREHOLDERS EQUITY
Retained Earnings	$10.78B	$9.685B
YoY Change	11.27%	8.72%
Common Stock	$408.6M	$408.6M
YoY Change	0.0%	0.0%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$2.174B	$1.392B
YoY Change	56.13%	27.23%
Treasury Stock Shares	26.16M shares	19.04M shares
Shareholders Equity	$10.51B	$10.22B	$10.22B
YoY Change
Total Liabilities & Shareholders Equity	$132.2B	$138.6B	$138.6B
YoY Change	-4.6%	11.83%	11.83%

Cashflow Statement

Concept	2018 Q4	2017 Q4	2017
OPERATING ACTIVITIES
Net Income	$409.9M	$356.6M	$1.199B
YoY Change	14.95%	33.81%	16.13%
Depreciation, Depletion And Amortization	$114.0M	$110.5M	$421.7M
YoY Change	3.17%	14.39%	12.97%
Cash From Operating Activities	$459.1M	$850.7M	$1.720B
YoY Change	-46.03%	1.45%	13.93%
INVESTING ACTIVITIES
Capital Expenditures	-$177.9M	-$120.9M	$91.60M
YoY Change	47.15%	-26.73%	-17.7%
Acquisitions
YoY Change
Other Investing Activities	-$843.2M	-$7.935B	-$25.80M
YoY Change	-89.37%	66.2%	-88.61%
Cash From Investing Activities	-$1.021B	-$8.056B	-$14.02B
YoY Change	-87.32%	63.09%	37.57%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net			$523.1M
YoY Change			27.24%
Debt Paid & Issued, Net			$208.7M
YoY Change			3014.93%
Cash From Financing Activities	77.80M	6.436B	$11.25B
YoY Change	-98.79%	36.49%	49.3%
NET CHANGE
Cash From Operating Activities	459.1M	850.7M	$1.720B
Cash From Investing Activities	-1.021B	-8.056B	-$14.02B
Cash From Financing Activities	77.80M	6.436B	$11.25B
Net Change In Cash	-484.2M	-769.1M	-$813.9M
YoY Change	-37.04%	-225.16%	-28.93%
FREE CASH FLOW
Cash From Operating Activities	$459.1M	$850.7M	$1.720B
Capital Expenditures	-$177.9M	-$120.9M	$91.60M
Free Cash Flow	$637.0M	$971.6M	$1.629B
YoY Change	-34.44%	-3.18%	16.45%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2019	dei	Amendment Flag AmendmentFlag	false
CY2019	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2019	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2018Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	560000000	shares
CY2018Q4	us-gaap	Preferred Stock No Par Value PreferredStockNoParValue
CY2019Q4	us-gaap	Preferred Stock No Par Value PreferredStockNoParValue
CY2019	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2019
CY2019	dei	Entity Central Index Key EntityCentralIndexKey	0000073124
CY2018	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
CY2018Q4	us-gaap	Collateral Securities Repledged Delivered Or Used CollateralSecuritiesRepledgedDeliveredOrUsed	0	USD
CY2017	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.60
CY2018	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.94
CY2019	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	2.60
CY2018Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	1.6667
CY2019Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	1.6667
CY2019Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	560000000	shares
CY2017	us-gaap	Gain Loss On Discontinuation Of Cash Flow Hedge Due To Forecasted Transaction Probable Of Not Occurring Net GainLossOnDiscontinuationOfCashFlowHedgeDueToForecastedTransactionProbableOfNotOccurringNet	0	USD
CY2018	us-gaap	Gain Loss On Discontinuation Of Cash Flow Hedge Due To Forecasted Transaction Probable Of Not Occurring Net GainLossOnDiscontinuationOfCashFlowHedgeDueToForecastedTransactionProbableOfNotOccurringNet	0	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Deferred Income LoansAndLeasesReceivableDeferredIncome	13200000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Deferred Income LoansAndLeasesReceivableDeferredIncome	14100000	USD
CY2018Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	10000000	shares
CY2018Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	26159474	shares
CY2019Q4	us-gaap	Treasury Stock Shares TreasuryStockShares	35462478	shares
CY2019	dei	Document Type DocumentType	10-K
CY2019	dei	Document Annual Report DocumentAnnualReport	true
CY2019	dei	Document Period End Date DocumentPeriodEndDate	2019-12-31
CY2019	dei	Document Transition Report DocumentTransitionReport	false
CY2019	dei	Entity File Number EntityFileNumber	001-36609
CY2019	dei	Entity Registrant Name EntityRegistrantName	NORTHERN TRUST CORPORATION
CY2019	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	DE
CY2019	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	36-2723087
CY2019	dei	Entity Address Address Line1 EntityAddressAddressLine1	50 South La Salle Street
CY2019	dei	Entity Address City Or Town EntityAddressCityOrTown	Chicago,
CY2019	dei	Entity Address State Or Province EntityAddressStateOrProvince	IL
CY2019	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	60603
CY2019	dei	City Area Code CityAreaCode	312
CY2019	dei	Local Phone Number LocalPhoneNumber	630-6000
CY2019	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes
CY2019	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2019	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2019	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2019	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2019Q2	dei	Entity Public Float EntityPublicFloat	19200000000	USD
CY2019	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
CY2019	dei	Entity Small Business EntitySmallBusiness	false
CY2019	dei	Entity Shell Company EntityShellCompany	false
CY2019Q4	us-gaap	Marketable Securities MarketableSecurities	51161100000	USD
CY2018Q4	us-gaap	Marketable Securities MarketableSecurities	51243100000	USD
CY2018Q4	us-gaap	Trading Securities TradingSecurities	300000	USD
CY2020Q1	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	209247666	shares
CY2019Q4	us-gaap	Cash And Due From Banks CashAndDueFromBanks	4459200000	USD
CY2018Q4	us-gaap	Cash And Due From Banks CashAndDueFromBanks	4581600000	USD
CY2019Q4	ntrs	Federal Reserve And Foreign Central Bank Deposits FederalReserveAndForeignCentralBankDeposits	33886000000.0	USD
CY2018Q4	ntrs	Federal Reserve And Foreign Central Bank Deposits FederalReserveAndForeignCentralBankDeposits	30080200000	USD
CY2019Q4	us-gaap	Interest Bearing Deposits In Banks InterestBearingDepositsInBanks	4877100000	USD
CY2018Q4	us-gaap	Interest Bearing Deposits In Banks InterestBearingDepositsInBanks	4264200000	USD
CY2019Q4	us-gaap	Federal Funds Sold And Securities Purchased Under Agreements To Resell FederalFundsSoldAndSecuritiesPurchasedUnderAgreementsToResell	712800000	USD
CY2018Q4	us-gaap	Federal Funds Sold And Securities Purchased Under Agreements To Resell FederalFundsSoldAndSecuritiesPurchasedUnderAgreementsToResell	1165200000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	38876300000	USD
CY2018Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	36888800000	USD
CY2019Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	12284500000	USD
CY2018Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	14354000000.0	USD
CY2019Q4	us-gaap	Trading Securities TradingSecurities	300000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	31409600000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	32490000000.0	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	104500000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	112600000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	483300000	USD
CY2018Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	428200000	USD
CY2019Q4	ntrs	Client Security Settlement Receivables ClientSecuritySettlementReceivables	845700000	USD
CY2018Q4	ntrs	Client Security Settlement Receivables ClientSecuritySettlementReceivables	1646100000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	696800000	USD
CY2018Q4	us-gaap	Goodwill Goodwill	669300000	USD
CY2019Q4	us-gaap	Other Assets OtherAssets	8401300000	USD
CY2018Q4	us-gaap	Other Assets OtherAssets	5757200000	USD
CY2019Q4	us-gaap	Assets Assets	136828400000	USD
CY2018Q4	us-gaap	Assets Assets	132212500000	USD
CY2019Q4	us-gaap	Noninterest Bearing Deposit Liabilities Domestic NoninterestBearingDepositLiabilitiesDomestic	14114700000	USD
CY2018Q4	us-gaap	Noninterest Bearing Deposit Liabilities Domestic NoninterestBearingDepositLiabilitiesDomestic	14508000000.0	USD
CY2019Q4	us-gaap	Deposits Savings Deposits DepositsSavingsDeposits	21441500000	USD
CY2018Q4	us-gaap	Deposits Savings Deposits DepositsSavingsDeposits	14612000000.0	USD
CY2019Q4	us-gaap	Time Deposits TimeDeposits	986700000	USD
CY2018Q4	us-gaap	Time Deposits TimeDeposits	688700000	USD
CY2019Q4	us-gaap	Noninterest Bearing Deposit Liabilities Foreign NoninterestBearingDepositLiabilitiesForeign	12177400000	USD
CY2018Q4	us-gaap	Noninterest Bearing Deposit Liabilities Foreign NoninterestBearingDepositLiabilitiesForeign	8220100000	USD
CY2019Q4	us-gaap	Interest Bearing Deposit Liabilities Foreign InterestBearingDepositLiabilitiesForeign	60400300000	USD
CY2018Q4	us-gaap	Interest Bearing Deposit Liabilities Foreign InterestBearingDepositLiabilitiesForeign	66468000000.0	USD
CY2019Q4	us-gaap	Deposits Deposits	109120600000	USD
CY2018Q4	us-gaap	Deposits Deposits	104496800000	USD
CY2019Q4	us-gaap	Federal Funds Purchased FederalFundsPurchased	552900000	USD
CY2018Q4	us-gaap	Federal Funds Purchased FederalFundsPurchased	2594200000	USD
CY2019Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	489700000	USD
CY2018Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	168300000	USD
CY2019Q4	us-gaap	Other Borrowings OtherBorrowings	6744800000	USD
CY2018Q4	us-gaap	Other Borrowings OtherBorrowings	7901700000	USD
CY2019Q4	us-gaap	Senior Notes SeniorNotes	2573000000.0	USD
CY2018Q4	us-gaap	Senior Notes SeniorNotes	2011300000	USD
CY2019Q4	us-gaap	Subordinated Debt SubordinatedDebt	1148100000	USD
CY2018Q4	us-gaap	Subordinated Debt SubordinatedDebt	1112400000	USD
CY2019Q4	ntrs	Trust Preferred Securities TrustPreferredSecurities	277700000	USD
CY2018Q4	ntrs	Trust Preferred Securities TrustPreferredSecurities	277600000	USD
CY2019Q4	us-gaap	Other Liabilities OtherLiabilities	4830600000	USD
CY2018Q4	us-gaap	Other Liabilities OtherLiabilities	3141900000	USD
CY2019Q4	us-gaap	Liabilities Liabilities	125737400000	USD
CY2018Q4	us-gaap	Liabilities Liabilities	121704200000	USD
CY2019Q4	us-gaap	Common Stock Value CommonStockValue	408600000	USD
CY2018Q4	us-gaap	Common Stock Value CommonStockValue	408600000	USD
CY2019Q4	us-gaap	Additional Paid In Capital AdditionalPaidInCapital	1013100000	USD
CY2018Q4	us-gaap	Additional Paid In Capital AdditionalPaidInCapital	1068500000	USD
CY2019Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	11656700000	USD
CY2018Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	10776800000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-194700000	USD
CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-453700000	USD
CY2019Q4	us-gaap	Treasury Stock Value TreasuryStockValue	3066100000	USD
CY2018Q4	us-gaap	Treasury Stock Value TreasuryStockValue	2173900000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	11091000000.0	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	10508300000	USD
CY2019Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	136828400000	USD
CY2018Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	132212500000	USD
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3852100000	USD
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3753700000	USD
CY2017	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3434300000	USD
CY2019	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	250900000	USD
CY2018	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	307200000	USD
CY2017	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	209900000	USD
CY2019	ntrs	Treasury Management Fees TreasuryManagementFees	44500000	USD
CY2018	ntrs	Treasury Management Fees TreasuryManagementFees	51800000	USD
CY2017	ntrs	Treasury Management Fees TreasuryManagementFees	56400000	USD
CY2018	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	127500000	USD
CY2019	ntrs	Security Commissionsand Trading Income SecurityCommissionsandTradingIncome	103600000	USD
CY2018	ntrs	Security Commissionsand Trading Income SecurityCommissionsandTradingIncome	98300000	USD
CY2017	ntrs	Security Commissionsand Trading Income SecurityCommissionsandTradingIncome	89600000	USD
CY2019	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	145500000	USD
CY2017	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	157500000	USD
CY2017	us-gaap	Noninterest Income NoninterestIncome	3946100000	USD
CY2019	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	2499900000	USD
CY2019	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1400000	USD
CY2018	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1000000.0	USD
CY2017	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1600000	USD
CY2019	us-gaap	Noninterest Income NoninterestIncome	4395200000	USD
CY2018	us-gaap	Noninterest Income NoninterestIncome	4337500000	USD
CY2018	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	2321400000	USD
CY2017	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	1769400000	USD
CY2019	us-gaap	Interest Expense InterestExpense	822000000.0	USD
CY2018	us-gaap	Interest Expense InterestExpense	698700000	USD
CY2017	us-gaap	Interest Expense InterestExpense	340200000	USD
CY2019	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	1677900000	USD
CY2018	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	1622700000	USD
CY2017	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	1429200000	USD
CY2019	ntrs	Provision For Recovery Of Loan And Lease Losses ProvisionForRecoveryOfLoanAndLeaseLosses	-14500000	USD
CY2018	ntrs	Provision For Recovery Of Loan And Lease Losses ProvisionForRecoveryOfLoanAndLeaseLosses	-14500000	USD
CY2017	ntrs	Provision For Recovery Of Loan And Lease Losses ProvisionForRecoveryOfLoanAndLeaseLosses	-28000000.0	USD
CY2019	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	1692400000	USD
CY2018	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	1637200000	USD
CY2017	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	1457200000	USD
CY2019	ntrs	Salaries Wages And Incentives SalariesWagesAndIncentives	1859000000.0	USD
CY2018	ntrs	Salaries Wages And Incentives SalariesWagesAndIncentives	1806900000	USD
CY2017	ntrs	Salaries Wages And Incentives SalariesWagesAndIncentives	1733700000	USD
CY2019	ntrs	Employee Benefits EmployeeBenefits	355200000	USD
CY2018	ntrs	Employee Benefits EmployeeBenefits	356700000	USD
CY2017	ntrs	Employee Benefits EmployeeBenefits	319900000	USD
CY2019	us-gaap	Professional Fees ProfessionalFees	774500000	USD
CY2018	us-gaap	Professional Fees ProfessionalFees	739400000	USD
CY2017	us-gaap	Professional Fees ProfessionalFees	668400000	USD
CY2019	ntrs	Equipment And Software Expense EquipmentAndSoftwareExpense	612100000	USD
CY2018	ntrs	Equipment And Software Expense EquipmentAndSoftwareExpense	582200000	USD
CY2017	ntrs	Equipment And Software Expense EquipmentAndSoftwareExpense	524000000.0	USD
CY2019	us-gaap	Occupancy Net OccupancyNet	212900000	USD
CY2018	us-gaap	Occupancy Net OccupancyNet	201100000	USD
CY2017	us-gaap	Occupancy Net OccupancyNet	191800000	USD
CY2019	us-gaap	Other Noninterest Expense OtherNoninterestExpense	329800000	USD
CY2018	us-gaap	Other Noninterest Expense OtherNoninterestExpense	330600000	USD
CY2017	us-gaap	Other Noninterest Expense OtherNoninterestExpense	331600000	USD
CY2019	us-gaap	Noninterest Expense NoninterestExpense	4143500000	USD
CY2018	us-gaap	Noninterest Expense NoninterestExpense	4016900000	USD
CY2017	us-gaap	Noninterest Expense NoninterestExpense	3769400000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	1944100000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	1957800000	USD
CY2017	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	1633900000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	451900000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	1492200000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	401400000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	434900000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	1556400000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	1199000000.0	USD
CY2019	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	46400000	USD
CY2018	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	46400000	USD
CY2017	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	49800000	USD
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	1445800000	USD
CY2018	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	1510000000.0	USD
CY2017	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	1149200000	USD
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	6.66
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	6.68
CY2017	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.95
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	6.63
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	6.64
CY2017	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.92
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	214525547	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	223148335	shares
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	228257664	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	215601149	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	224488326	shares
CY2017	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	229654401	shares
CY2019	ntrs	Other Than Temporary Impairment Losses OtherThanTemporaryImpairmentLosses	300000	USD
CY2018	ntrs	Other Than Temporary Impairment Losses OtherThanTemporaryImpairmentLosses	500000	USD
CY2017	ntrs	Other Than Temporary Impairment Losses OtherThanTemporaryImpairmentLosses	200000	USD
CY2019	ntrs	Investment Security Gains Losses Net InvestmentSecurityGainsLossesNet	-1100000	USD
CY2018	ntrs	Investment Security Gains Losses Net InvestmentSecurityGainsLossesNet	-500000	USD
CY2017	ntrs	Investment Security Gains Losses Net InvestmentSecurityGainsLossesNet	-1400000	USD
CY2019	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1400000	USD
CY2018	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1000000.0	USD
CY2017	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1600000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	1492200000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	1556400000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	1199000000.0	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	228900000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-22300000	USD
CY2017	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-42400000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax Parent OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent	-7700000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax Parent OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent	-1400000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax Parent OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent	-1600000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	49900000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	22200000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	16700000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	12100000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	12600000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	17000000.0	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	259000000.0	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-14100000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-44300000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	1751200000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	1542300000	USD
CY2017	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	1154700000	USD
CY2016Q4	us-gaap	Stockholders Equity StockholdersEquity	9770400000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	1199000000.0	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-44300000	USD
CY2017	us-gaap	Dividends Common Stock DividendsCommonStock	372500000	USD
CY2017	us-gaap	Dividends Preferred Stock DividendsPreferredStock	49800000	USD
CY2017	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	225100000	USD
CY2017	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	523100000	USD
CY2017	us-gaap	Stock Issued During Period Value Treasury Stock Reissued StockIssuedDuringPeriodValueTreasuryStockReissued	-117100000	USD
CY2017	us-gaap	Amortization Of Esop Award AmortizationOfESOPAward	128500000	USD
CY2017Q4	us-gaap	Stockholders Equity StockholdersEquity	10216200000	USD
CY2018	us-gaap	Tax Cuts And Jobs Act Of2017 Reclassification From Aoci To Retained Earnings Tax Effect TaxCutsAndJobsActOf2017ReclassificationFromAociToRetainedEarningsTaxEffect	0	USD
CY2018Q1	us-gaap	Cumulative Effect Of New Accounting Principle In Period Of Adoption CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	-4500000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	1556400000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-14100000	USD
CY2018	us-gaap	Dividends Common Stock DividendsCommonStock	439100000	USD
CY2018	us-gaap	Dividends Preferred Stock DividendsPreferredStock	46400000	USD
CY2018	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	142800000	USD
CY2018	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	924300000	USD
CY2018	us-gaap	Stock Issued During Period Value Treasury Stock Reissued StockIssuedDuringPeriodValueTreasuryStockReissued	-110200000	USD
CY2018	us-gaap	Amortization Of Esop Award AmortizationOfESOPAward	131500000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	10508300000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	1492200000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	259000000.0	USD
CY2019	us-gaap	Dividends Common Stock DividendsCommonStock	565900000	USD
CY2019	us-gaap	Dividends Preferred Stock DividendsPreferredStock	46400000	USD
CY2019	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	391400000	USD
CY2019	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	208000000.0	USD
CY2019	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	1100200000	USD
CY2019	us-gaap	Stock Issued During Period Value Treasury Stock Reissued StockIssuedDuringPeriodValueTreasuryStockReissued	-163900000	USD
CY2019	us-gaap	Amortization Of Esop Award AmortizationOfESOPAward	108500000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	11091000000.0	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	1492200000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	1556400000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	1199000000.0	USD
CY2019	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1400000	USD
CY2018	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1000000.0	USD
CY2017	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1600000	USD
CY2019	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-64600000	USD
CY2018	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-95900000	USD
CY2017	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-105000000.0	USD
CY2019	ntrs	Provision For Recovery Of Loan And Lease Losses ProvisionForRecoveryOfLoanAndLeaseLosses	-14500000	USD
CY2018	ntrs	Provision For Recovery Of Loan And Lease Losses ProvisionForRecoveryOfLoanAndLeaseLosses	-14500000	USD
CY2017	ntrs	Provision For Recovery Of Loan And Lease Losses ProvisionForRecoveryOfLoanAndLeaseLosses	-28000000.0	USD
CY2019	us-gaap	Depreciation Nonproduction DepreciationNonproduction	103200000	USD
CY2018	us-gaap	Depreciation Nonproduction DepreciationNonproduction	108600000	USD
CY2017	us-gaap	Depreciation Nonproduction DepreciationNonproduction	101200000	USD
CY2019	us-gaap	Capitalized Computer Software Amortization1 CapitalizedComputerSoftwareAmortization1	339100000	USD
CY2018	us-gaap	Capitalized Computer Software Amortization1 CapitalizedComputerSoftwareAmortization1	334900000	USD
CY2017	us-gaap	Capitalized Computer Software Amortization1 CapitalizedComputerSoftwareAmortization1	309100000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	16600000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	17400000	USD
CY2017	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	11400000	USD
CY2019	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	-70700000	USD
CY2018	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	-130000000.0	USD
CY2017	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	36200000	USD
CY2019	us-gaap	Pension Contributions PensionContributions	6100000	USD
CY2018	us-gaap	Pension Contributions PensionContributions	74500000	USD
CY2017	us-gaap	Pension Contributions PensionContributions	14500000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	34300000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	10500000	USD
CY2017	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-76100000	USD
CY2019	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	50300000	USD
CY2018	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	197000000.0	USD
CY2017	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	119300000	USD
CY2019	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	-23600000	USD
CY2018	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	28500000	USD
CY2017	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	10700000	USD
CY2019	us-gaap	Increase Decrease In Derivative Assets IncreaseDecreaseInDerivativeAssets	-1154000000.0	USD
CY2018	us-gaap	Increase Decrease In Derivative Assets IncreaseDecreaseInDerivativeAssets	699600000	USD
CY2017	us-gaap	Increase Decrease In Derivative Assets IncreaseDecreaseInDerivativeAssets	-486200000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	448200000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-729900000	USD
CY2017	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	302100000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	2592000000.0	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	1767500000	USD
CY2017	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	1720400000	USD
CY2019	us-gaap	Proceeds From Payments For Federal Funds Sold And Securities Purchased Under Agreements To Resell Net ProceedsFromPaymentsForFederalFundsSoldAndSecuritiesPurchasedUnderAgreementsToResellNet	486300000	USD
CY2018	us-gaap	Proceeds From Payments For Federal Funds Sold And Securities Purchased Under Agreements To Resell Net ProceedsFromPaymentsForFederalFundsSoldAndSecuritiesPurchasedUnderAgreementsToResellNet	105700000	USD
CY2017	us-gaap	Proceeds From Payments For Federal Funds Sold And Securities Purchased Under Agreements To Resell Net ProceedsFromPaymentsForFederalFundsSoldAndSecuritiesPurchasedUnderAgreementsToResellNet	678900000	USD
CY2019	us-gaap	Proceeds From Payments For In Interest Bearing Deposits In Banks ProceedsFromPaymentsForInInterestBearingDepositsInBanks	-614600000	USD
CY2018	us-gaap	Proceeds From Payments For In Interest Bearing Deposits In Banks ProceedsFromPaymentsForInInterestBearingDepositsInBanks	1073800000	USD
CY2017	us-gaap	Proceeds From Payments For In Interest Bearing Deposits In Banks ProceedsFromPaymentsForInInterestBearingDepositsInBanks	-467700000	USD
CY2019	ntrs	Payments For Proceeds From Federal Reserve And Foreign Central Bank Deposits PaymentsForProceedsFromFederalReserveAndForeignCentralBankDeposits	3683200000	USD
CY2018	ntrs	Payments For Proceeds From Federal Reserve And Foreign Central Bank Deposits PaymentsForProceedsFromFederalReserveAndForeignCentralBankDeposits	-9679600000	USD
CY2017	ntrs	Payments For Proceeds From Federal Reserve And Foreign Central Bank Deposits PaymentsForProceedsFromFederalReserveAndForeignCentralBankDeposits	12748700000	USD
CY2019	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	14154300000	USD
CY2018	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	21463100000	USD
CY2017	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	11955200000	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	16290900000	USD
CY2018	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	20036700000	USD
CY2017	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	9924800000	USD
CY2019	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	12811000000.0	USD
CY2018	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	12596900000	USD
CY2017	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	9780000000.0	USD
CY2019	us-gaap	Proceeds From Sale And Maturity Of Available For Sale Securities ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities	11057200000	USD
CY2018	us-gaap	Proceeds From Sale And Maturity Of Available For Sale Securities ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities	8958700000	USD
CY2017	us-gaap	Proceeds From Sale And Maturity Of Available For Sale Securities ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities	10103400000	USD
CY2019	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	-1087900000	USD
CY2018	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	-66100000	USD
CY2017	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	-1451000000.0	USD
CY2019	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	158000000.0	USD
CY2018	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	97600000	USD
CY2017	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	91600000	USD
CY2019	us-gaap	Payments For Software PaymentsForSoftware	441800000	USD
CY2018	us-gaap	Payments For Software PaymentsForSoftware	408400000	USD
CY2017	us-gaap	Payments For Software PaymentsForSoftware	381200000	USD
CY2019	ntrs	Net Change In Client Security Settlement Receivables NetChangeInClientSecuritySettlementReceivables	-821000000.0	USD
CY2018	ntrs	Net Change In Client Security Settlement Receivables NetChangeInClientSecuritySettlementReceivables	49700000	USD
CY2017	ntrs	Net Change In Client Security Settlement Receivables NetChangeInClientSecuritySettlementReceivables	592600000	USD
CY2019	us-gaap	Payments To Acquire Interest In Subsidiaries And Affiliates PaymentsToAcquireInterestInSubsidiariesAndAffiliates	10500000	USD
CY2018	us-gaap	Payments To Acquire Interest In Subsidiaries And Affiliates PaymentsToAcquireInterestInSubsidiariesAndAffiliates	104200000	USD
CY2017	us-gaap	Payments To Acquire Interest In Subsidiaries And Affiliates PaymentsToAcquireInterestInSubsidiariesAndAffiliates	188500000	USD
CY2019	us-gaap	Payments To Acquire Life Insurance Policies PaymentsToAcquireLifeInsurancePolicies	1500000000.0	USD
CY2018	us-gaap	Payments To Acquire Life Insurance Policies PaymentsToAcquireLifeInsurancePolicies	0	USD
CY2017	us-gaap	Payments To Acquire Life Insurance Policies PaymentsToAcquireLifeInsurancePolicies	0	USD
CY2019	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-225100000	USD
CY2018	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	873600000	USD
CY2017	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	-25800000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-3405000000.0	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	4327100000	USD
CY2017	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-14021600000	USD
CY2019	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	4263600000	USD
CY2018	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	-6163200000	USD
CY2017	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	8523600000	USD
CY2019	us-gaap	Increase Decrease In Federal Funds Purchased And Securities Sold Under Agreements To Repurchase Net IncreaseDecreaseInFederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseNet	-2041300000	USD
CY2018	us-gaap	Increase Decrease In Federal Funds Purchased And Securities Sold Under Agreements To Repurchase Net IncreaseDecreaseInFederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseNet	308100000	USD
CY2017	us-gaap	Increase Decrease In Federal Funds Purchased And Securities Sold Under Agreements To Repurchase Net IncreaseDecreaseInFederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseNet	2081200000	USD
CY2019	us-gaap	Proceeds From Payments For In Securities Sold Under Agreements To Repurchase ProceedsFromPaymentsForInSecuritiesSoldUnderAgreementsToRepurchase	320900000	USD
CY2018	us-gaap	Proceeds From Payments For In Securities Sold Under Agreements To Repurchase ProceedsFromPaymentsForInSecuritiesSoldUnderAgreementsToRepurchase	-665200000	USD
CY2017	us-gaap	Proceeds From Payments For In Securities Sold Under Agreements To Repurchase ProceedsFromPaymentsForInSecuritiesSoldUnderAgreementsToRepurchase	360500000	USD
CY2019	us-gaap	Proceeds From Repayments Of Short Term Debt Maturing In Three Months Or Less ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	-1184500000	USD
CY2018	us-gaap	Proceeds From Repayments Of Short Term Debt Maturing In Three Months Or Less ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	1860900000	USD
CY2017	us-gaap	Proceeds From Repayments Of Short Term Debt Maturing In Three Months Or Less ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	967700000	USD
CY2019	us-gaap	Proceeds From Issuance Of Senior Long Term Debt ProceedsFromIssuanceOfSeniorLongTermDebt	498000000.0	USD
CY2018	us-gaap	Proceeds From Issuance Of Senior Long Term Debt ProceedsFromIssuanceOfSeniorLongTermDebt	497900000	USD
CY2017	us-gaap	Proceeds From Issuance Of Senior Long Term Debt ProceedsFromIssuanceOfSeniorLongTermDebt	350000000.0	USD
CY2019	us-gaap	Proceeds From Repayments Of Debt ProceedsFromRepaymentsOfDebt	0	USD
CY2018	us-gaap	Proceeds From Repayments Of Debt ProceedsFromRepaymentsOfDebt	-314300000	USD
CY2017	us-gaap	Proceeds From Repayments Of Debt ProceedsFromRepaymentsOfDebt	-208700000	USD
CY2019	us-gaap	Proceeds From Issuance Of Preferred Stock And Preference Stock ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	392500000	USD
CY2018	us-gaap	Proceeds From Issuance Of Preferred Stock And Preference Stock ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	0	USD
CY2017	us-gaap	Proceeds From Issuance Of Preferred Stock And Preference Stock ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	0	USD
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	1100200000	USD
CY2018	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	924300000	USD
CY2017	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	523100000	USD
CY2019	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	44000000.0	USD
CY2018	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	32600000	USD
CY2017	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	108000000.0	USD
CY2019	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	529700000	USD
CY2018	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	405400000	USD
CY2017	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	356800000	USD
CY2019	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	46400000	USD
CY2018	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	46400000	USD
CY2017	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	49800000	USD
CY2019	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	-1000000.0	USD
CY2018	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	1100000	USD
CY2017	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	100000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	615900000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-5818200000	USD
CY2017	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	11252700000	USD
CY2019	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	74700000	USD
CY2018	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	-212900000	USD
CY2017	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	234600000	USD
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-122400000	USD
CY2018	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	63500000	USD
CY2017	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-813900000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	4581600000	USD
CY2017Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	4518100000	USD
CY2016Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	5332000000.0	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	4459200000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	4581600000	USD
CY2017Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	4518100000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	845500000	USD
CY2018	us-gaap	Interest Paid Net InterestPaidNet	670200000	USD
CY2017	us-gaap	Interest Paid Net InterestPaidNet	328800000	USD
CY2019	us-gaap	Income Taxes Paid IncomeTaxesPaid	437000000.0	USD
CY2018	us-gaap	Income Taxes Paid IncomeTaxesPaid	493500000	USD
CY2017	us-gaap	Income Taxes Paid IncomeTaxesPaid	441200000	USD
CY2019	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	3500000	USD
CY2018	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	11400000	USD
CY2017	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	8200000	USD
CY2019	us-gaap	Transfer Of Portfolio Loans And Leases To Held For Sale1 TransferOfPortfolioLoansAndLeasesToHeldForSale1	53600000	USD
CY2018	us-gaap	Transfer Of Portfolio Loans And Leases To Held For Sale1 TransferOfPortfolioLoansAndLeasesToHeldForSale1	0	USD
CY2017	us-gaap	Transfer Of Portfolio Loans And Leases To Held For Sale1 TransferOfPortfolioLoansAndLeasesToHeldForSale1	0	USD
CY2019	ntrs	Numberof Client Focused Reportable Segment NumberofClientFocusedReportableSegment	2	Segment
CY2019	us-gaap	Use Of Estimates UseOfEstimates	Use of Estimates in the Preparation of Financial Statements.<span style="font-family:inherit;font-size:10pt;"> The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions in the application of certain of our significant accounting policies that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expense during the reporting period. Actual results could differ from those estimates.</span>
CY2019Q4	ntrs	Smaller Homogeneous Loan Threshold SmallerHomogeneousLoanThreshold	1000000	USD
CY2019	us-gaap	Description Of New Accounting Pronouncements Not Yet Adopted DescriptionOfNewAccountingPronouncementsNotYetAdopted	Recent Accounting Pronouncements<div style="line-height:120%;text-align:justify;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">On January 1, 2019, Northern Trust adopted ASU No. 2016-02, “Leases (Topic 842)" (ASU 2016-02). ASU 2016-02 introduces a lessee model that brings most leases on the balance sheet, with certain specified scope exceptions. Specifically within the lessee model under ASU 2016-02, a lessee is required </span><span style="font-family:inherit;font-size:10pt;">to recognize on the balance sheet a liability to make future lease payments, known as the lease liability, and a right-of-use asset (ROU asset)</span><span style="font-family:inherit;font-size:10pt;"> representing its right to use the underlying asset over the lease term. Upon adoption, Northern Trust elected the package of practical expedients available under ASU 2016-02, which allowed Northern Trust to forego a reassessment of (1) whether any expired or existing contracts are or contain leases, (2) lease classification for any expired or existing leases, and (3) the initial direct costs for any existing leases. </span><span style="font-family:inherit;font-size:10pt;">As a result of adopting ASU 2016-02, Northern Trust recognized operating lease liabilities and ROU assets of approximately</span><span style="font-family:inherit;font-size:10pt;"> </span><span style="font-family:inherit;font-size:10pt;"><span>$530 million</span></span><span style="font-family:inherit;font-size:10pt;"> and </span><span style="font-family:inherit;font-size:10pt;"><span>$480 million</span></span><span style="font-family:inherit;font-size:10pt;">, respectively. </span><span style="font-family:inherit;font-size:10pt;">Northern Trust did not restate comparative periods for the effects of applying ASU 2016-02. There was no significant impact to Northern Trust’s consolidated results of operations.</span><span style="font-family:inherit;font-size:10pt;"> Please refer to Note 10, “Lease Commitments” for further information. </span></div><div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">On January 1, 2019, Northern Trust adopted ASU No. 2017-08, “Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Securities” (ASU 2017-08). </span><span style="font-family:inherit;font-size:10pt;">ASU 2017-08 amends the amortization period for certain callable debt securities held at a premium and shortens the amortization period for the premium to the earliest call date. Upon adoption of ASU 2017-08, there was no significant impact to Northern Trust’s consolidated financial condition or results of operations.</span><span style="font-family:inherit;font-size:10pt;"> </span></div><span style="font-family:inherit;font-size:10pt;">On January 1, 2019, Northern Trust adopted ASU No. 2018-16, “Derivatives and Hedging (Topic 815): Inclusion of the Secured Overnight Financing Rate (SOFR) Overnight Index Swap (OIS) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes” (ASU 2018-16). </span><span style="font-family:inherit;font-size:10pt;">ASU 2018-16 permits use of the OIS rate based on SOFR as a U.S. benchmark interest rate for hedge accounting purposes under Topic 815. Upon adoption of ASU 2018-16, there was no significant impact to Northern Trust’s consolidated financial condition or results of operations.</span>
CY2019Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	38722200000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	262700000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	108600000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	38876300000	USD
CY2018Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	37041800000	USD
CY2018Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	98400000	USD
CY2018Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	251400000	USD
CY2018Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	36888800000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	8870500000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	8882100000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	18195700000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	18311700000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	8977400000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	9005200000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	2678600000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	2677300000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	38722200000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	38876300000	USD
CY2019Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	12284500000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	45700000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	80900000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	12249300000	USD
CY2018Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	14354000000.0	USD
CY2018Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	18700000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	105700000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	14267000000.0	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	4554300000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	4556400000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	7309700000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	7333100000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount	317300000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	310700000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	103200000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	49100000	USD
CY2019Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	12284500000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	12249300000	USD
CY2019Q4	ntrs	Held To Maturity Securities Transferred From Available For Sale HeldToMaturitySecuritiesTransferredFromAvailableForSale	160800000	USD
CY2018Q4	ntrs	Held To Maturity Securities Transferred From Available For Sale HeldToMaturitySecuritiesTransferredFromAvailableForSale	287900000	USD
CY2019	ntrs	Proceeds From Sales Of Investment Securities ProceedsFromSalesOfInvestmentSecurities	1200000000	USD
CY2018	ntrs	Proceeds From Sales Of Investment Securities ProceedsFromSalesOfInvestmentSecurities	307300000	USD
CY2017	ntrs	Proceeds From Sales Of Investment Securities ProceedsFromSalesOfInvestmentSecurities	2200000000	USD
CY2019	ntrs	Gross Realized Investment Gains GrossRealizedInvestmentGains	2400000	USD
CY2018	ntrs	Gross Realized Investment Gains GrossRealizedInvestmentGains	1500000	USD
CY2017	ntrs	Gross Realized Investment Gains GrossRealizedInvestmentGains	200000	USD
CY2019	ntrs	Gross Realized Investment Losses GrossRealizedInvestmentLosses	3500000	USD
CY2018	ntrs	Gross Realized Investment Losses GrossRealizedInvestmentLosses	2000000.0	USD
CY2017	ntrs	Gross Realized Investment Losses GrossRealizedInvestmentLosses	1600000	USD
CY2019	ntrs	Other Than Temporary Impairment Losses OtherThanTemporaryImpairmentLosses	300000	USD
CY2018	ntrs	Other Than Temporary Impairment Losses OtherThanTemporaryImpairmentLosses	500000	USD
CY2017	ntrs	Other Than Temporary Impairment Losses OtherThanTemporaryImpairmentLosses	200000	USD
CY2019	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1400000	USD
CY2018	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1000000.0	USD
CY2017	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1600000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	13362900000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	91200000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	10754400000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	98300000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	24117300000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	189500000	USD
CY2018Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	18648800000	USD
CY2018Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	83900000	USD
CY2018Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	15563400000	USD
CY2018Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	273200000	USD
CY2018Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	34212200000	USD
CY2018Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	357100000	USD
CY2019Q4	ntrs	Number Of Securities Unrealized Losses Position NumberOfSecuritiesUnrealizedLossesPosition	1289	Investment
CY2019Q4	ntrs	Securities Continuous Unrealized Loss Position Fair Value SecuritiesContinuousUnrealizedLossPositionFairValue	24100000000	USD
CY2019Q4	ntrs	Securities Continuous Unrealized Loss Position Aggregate Losses SecuritiesContinuousUnrealizedLossPositionAggregateLosses	189500000	USD
CY2019	ntrs	Other Than Temporary Impairment Losses OtherThanTemporaryImpairmentLosses	300000	USD
CY2018	ntrs	Other Than Temporary Impairment Losses OtherThanTemporaryImpairmentLosses	500000	USD
CY2017	ntrs	Other Than Temporary Impairment Losses OtherThanTemporaryImpairmentLosses	200000	USD
CY2019	ntrs	Other Than Temporary Impairment Losses OtherThanTemporaryImpairmentLosses	300000	USD
CY2018	ntrs	Other Than Temporary Impairment Losses OtherThanTemporaryImpairmentLosses	500000	USD
CY2017	ntrs	Other Than Temporary Impairment Losses OtherThanTemporaryImpairmentLosses	200000	USD
CY2019	us-gaap	Other Than Temporary Impairment Losses Investments Portion In Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherThanTemporaryImpairmentLossesInvestmentsPortionInOtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	0	USD
CY2018	us-gaap	Other Than Temporary Impairment Losses Investments Portion In Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherThanTemporaryImpairmentLossesInvestmentsPortionInOtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	0	USD
CY2017	us-gaap	Other Than Temporary Impairment Losses Investments Portion In Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherThanTemporaryImpairmentLossesInvestmentsPortionInOtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	0	USD
CY2019	ntrs	Other Than Temporary Impairment Losses Recognized In Earnings OtherThanTemporaryImpairmentLossesRecognizedInEarnings	300000	USD
CY2018	ntrs	Other Than Temporary Impairment Losses Recognized In Earnings OtherThanTemporaryImpairmentLossesRecognizedInEarnings	500000	USD
CY2017	ntrs	Other Than Temporary Impairment Losses Recognized In Earnings OtherThanTemporaryImpairmentLossesRecognizedInEarnings	200000	USD
CY2018Q4	us-gaap	Other Than Temporary Impairment Credit Losses Recognized In Earnings Credit Losses On Debt Securities Held OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld	4100000	USD
CY2017Q4	us-gaap	Other Than Temporary Impairment Credit Losses Recognized In Earnings Credit Losses On Debt Securities Held OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld	3600000	USD
CY2016Q4	us-gaap	Other Than Temporary Impairment Credit Losses Recognized In Earnings Credit Losses On Debt Securities Held OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld	3400000	USD
CY2019	us-gaap	Other Than Temporary Impairment Credit Losses Recognized In Earnings Additions No Previous Impairment OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsNoPreviousImpairment	200000	USD
CY2018	us-gaap	Other Than Temporary Impairment Credit Losses Recognized In Earnings Additions No Previous Impairment OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsNoPreviousImpairment	400000	USD
CY2017	us-gaap	Other Than Temporary Impairment Credit Losses Recognized In Earnings Additions No Previous Impairment OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsNoPreviousImpairment	100000	USD
CY2019	us-gaap	Other Than Temporary Impairment Credit Losses Recognized In Earnings Additions Additional Credit Losses OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsAdditionalCreditLosses	100000	USD
CY2018	us-gaap	Other Than Temporary Impairment Credit Losses Recognized In Earnings Additions Additional Credit Losses OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsAdditionalCreditLosses	100000	USD
CY2017	us-gaap	Other Than Temporary Impairment Credit Losses Recognized In Earnings Additions Additional Credit Losses OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsAdditionalCreditLosses	100000	USD
CY2019	us-gaap	Other Than Temporary Impairment Credit Losses Recognized In Earnings Reductions Securities Sold OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsReductionsSecuritiesSold	0	USD
CY2018	us-gaap	Other Than Temporary Impairment Credit Losses Recognized In Earnings Reductions Securities Sold OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsReductionsSecuritiesSold	0	USD
CY2017	us-gaap	Other Than Temporary Impairment Credit Losses Recognized In Earnings Reductions Securities Sold OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsReductionsSecuritiesSold	0	USD
CY2019Q4	us-gaap	Other Than Temporary Impairment Credit Losses Recognized In Earnings Credit Losses On Debt Securities Held OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld	4400000	USD
CY2018Q4	us-gaap	Other Than Temporary Impairment Credit Losses Recognized In Earnings Credit Losses On Debt Securities Held OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld	4100000	USD
CY2017Q4	us-gaap	Other Than Temporary Impairment Credit Losses Recognized In Earnings Credit Losses On Debt Securities Held OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld	3600000	USD
CY2019	us-gaap	Schedule Of Resale Agreements ScheduleOfResaleAgreements	<div style="line-height:120%;font-size:10pt;"><div style="padding-left:0px;text-indent:0px;line-height:normal;padding-top:10px;"><table cellpadding="0" cellspacing="0" style="font-family:Times New Roman;font-size:10pt;width:100%;border-collapse:collapse;text-align:left;"><tr><td colspan="7"/></tr><tr><td style="width:80%;"/><td style="width:1%;"/><td style="width:8%;"/><td style="width:1%;"/><td style="width:1%;"/><td style="width:8%;"/><td style="width:1%;"/></tr><tr><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="font-size:7pt;"><span style="font-family:inherit;font-size:7pt;">($ In Millions)</span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:7pt;"><span style="font-family:inherit;font-size:7pt;font-weight:bold;">2019</span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:7pt;"><span style="font-family:inherit;font-size:7pt;">2018</span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:top;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="font-size:8pt;"><span style="font-family:Times New Roman;font-size:8pt;">Balance at December 31</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;background-color:#cceeff;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">$</span></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>707.8</span></span></div></td><td style="vertical-align:bottom;background-color:#cceeff;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;background-color:#cceeff;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">$</span></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>1,031.2</span></span></div></td><td style="vertical-align:bottom;background-color:#cceeff;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:top;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="font-size:8pt;"><span style="font-family:Times New Roman;font-size:8pt;">Average Balance During the Year</span></div></td><td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>835.0</span></span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>1,478.3</span></span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:top;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="font-size:8pt;"><span style="font-family:Times New Roman;font-size:8pt;">Average Interest Rate Earned During the Year</span></div></td><td colspan="2" style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>2.10</span></span></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-right:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">%</span></div></td><td colspan="2" style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>2.22</span></span></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-right:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">%</span></div></td></tr><tr><td style="vertical-align:top;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="font-size:8pt;"><span style="font-family:Times New Roman;font-size:8pt;">Maximum Month-End Balance During the Year</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">$</span></div></td><td style="vertical-align:bottom;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>1,290.0</span></span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">$</span></div></td><td style="vertical-align:bottom;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>1,942.0</span></span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr></table></div><span style="font-family:inherit;font-size:10pt;"><br/></span></div>
CY2019Q4	us-gaap	Securities Purchased Under Agreements To Resell SecuritiesPurchasedUnderAgreementsToResell	707800000	USD
CY2018Q4	us-gaap	Securities Purchased Under Agreements To Resell SecuritiesPurchasedUnderAgreementsToResell	1031200000	USD
CY2019	ntrs	Securities Purchased Under Agreement To Resell Average Balance During Period SecuritiesPurchasedUnderAgreementToResellAverageBalanceDuringPeriod	835000000.0	USD
CY2018	ntrs	Securities Purchased Under Agreement To Resell Average Balance During Period SecuritiesPurchasedUnderAgreementToResellAverageBalanceDuringPeriod	1478300000	USD
CY2019	ntrs	Securities Purchased Under Agreement To Resell Average Interest Rate Earned During Period SecuritiesPurchasedUnderAgreementToResellAverageInterestRateEarnedDuringPeriod	0.0210
CY2018	ntrs	Securities Purchased Under Agreement To Resell Average Interest Rate Earned During Period SecuritiesPurchasedUnderAgreementToResellAverageInterestRateEarnedDuringPeriod	0.0222
CY2019	ntrs	Securities Purchased Under Agreement To Resell Maximum Month End Balance During Period SecuritiesPurchasedUnderAgreementToResellMaximumMonthEndBalanceDuringPeriod	1290000000.0	USD
CY2018	ntrs	Securities Purchased Under Agreement To Resell Maximum Month End Balance During Period SecuritiesPurchasedUnderAgreementToResellMaximumMonthEndBalanceDuringPeriod	1942000000.0	USD
CY2019	us-gaap	Schedule Of Repurchase Agreements ScheduleOfRepurchaseAgreements	<div style="line-height:120%;font-size:10pt;"><div style="padding-left:0px;text-indent:0px;line-height:normal;padding-top:10px;"><table cellpadding="0" cellspacing="0" style="font-family:Times New Roman;font-size:10pt;width:100%;border-collapse:collapse;text-align:left;"><tr><td colspan="7"/></tr><tr><td style="width:80%;"/><td style="width:1%;"/><td style="width:8%;"/><td style="width:1%;"/><td style="width:1%;"/><td style="width:8%;"/><td style="width:1%;"/></tr><tr><td style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="font-size:7pt;"><span style="font-family:inherit;font-size:7pt;">($ In Millions)</span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:7pt;"><span style="font-family:inherit;font-size:7pt;font-weight:bold;">2019</span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td colspan="2" style="vertical-align:bottom;border-bottom:1px solid #000000;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:7pt;"><span style="font-family:inherit;font-size:7pt;">2018</span></div></td><td style="vertical-align:bottom;border-bottom:1px solid #000000;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:top;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;border-top:1px solid #000000;"><div style="font-size:8pt;"><span style="font-family:Times New Roman;font-size:8pt;">Balance at December 31</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;background-color:#cceeff;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">$</span></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>489.7</span></span></div></td><td style="vertical-align:bottom;background-color:#cceeff;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;background-color:#cceeff;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">$</span></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>168.3</span></span></div></td><td style="vertical-align:bottom;background-color:#cceeff;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:top;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="font-size:8pt;"><span style="font-family:Times New Roman;font-size:8pt;">Average Balance During the Year</span></div></td><td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>339.0</span></span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td colspan="2" style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>525.2</span></span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr><tr><td style="vertical-align:top;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="font-size:8pt;"><span style="font-family:Times New Roman;font-size:8pt;">Average Interest Rate Paid During the Year</span></div></td><td colspan="2" style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>1.89</span></span></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-right:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">%</span></div></td><td colspan="2" style="vertical-align:bottom;background-color:#cceeff;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>1.48</span></span></div></td><td style="vertical-align:bottom;background-color:#cceeff;padding-right:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">%</span></div></td></tr><tr><td style="vertical-align:top;padding-left:2px;padding-top:2px;padding-bottom:2px;padding-right:2px;"><div style="font-size:8pt;"><span style="font-family:Times New Roman;font-size:8pt;">Maximum Month-End Balance During the Year</span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;">$</span></div></td><td style="vertical-align:bottom;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"><span>489.7</span></span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td><td style="vertical-align:bottom;padding-left:2px;padding-top:2px;padding-bottom:2px;"><div style="text-align:left;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;">$</span></div></td><td style="vertical-align:bottom;padding-top:2px;padding-bottom:2px;"><div style="text-align:right;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;"><span>981.3</span></span></div></td><td style="vertical-align:bottom;"><div style="text-align:left;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div></td></tr></table></div><span style="font-family:inherit;font-size:10pt;"><br/></span></div>
CY2019Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	489700000	USD
CY2018Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	168300000	USD
CY2019	ntrs	Securities Sold Under Agreements To Repurchase Average Balance During Period SecuritiesSoldUnderAgreementsToRepurchaseAverageBalanceDuringPeriod	339000000.0	USD
CY2018	ntrs	Securities Sold Under Agreements To Repurchase Average Balance During Period SecuritiesSoldUnderAgreementsToRepurchaseAverageBalanceDuringPeriod	525200000	USD
CY2019	ntrs	Securities Sold Under Agreements To Repurchase Average Interest Rate Paid During Period SecuritiesSoldUnderAgreementsToRepurchaseAverageInterestRatePaidDuringPeriod	0.0189
CY2018	ntrs	Securities Sold Under Agreements To Repurchase Average Interest Rate Paid During Period SecuritiesSoldUnderAgreementsToRepurchaseAverageInterestRatePaidDuringPeriod	0.0148
CY2019	ntrs	Securities Sold Under Agreements To Repurchase Maximum Month End Balance During Period SecuritiesSoldUnderAgreementsToRepurchaseMaximumMonthEndBalanceDuringPeriod	489700000	USD
CY2018	ntrs	Securities Sold Under Agreements To Repurchase Maximum Month End Balance During Period SecuritiesSoldUnderAgreementsToRepurchaseMaximumMonthEndBalanceDuringPeriod	981300000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	31409600000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	32490000000.0	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	104500000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	112600000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	31305100000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	32377400000	USD
CY2019Q4	ntrs	Lower Limit Of Generally Required Loan To Collateral Value For Residential Real Estate Loans LowerLimitOfGenerallyRequiredLoanToCollateralValueForResidentialRealEstateLoans	0.65
CY2019Q4	ntrs	Upper Limit Of Generally Required Loan To Collateral Value For Residential Real Estate Loans UpperLimitOfGenerallyRequiredLoanToCollateralValueForResidentialRealEstateLoans	0.80
CY2019	ntrs	Line Of Credit Draw Down Period LineOfCreditDrawDownPeriod	P10Y
CY2019Q4	ntrs	Loans Receivable Overdraft Advances LoansReceivableOverdraftAdvances	1100000000	USD
CY2018Q4	ntrs	Loans Receivable Overdraft Advances LoansReceivableOverdraftAdvances	2200000000	USD
CY2019Q4	ntrs	Overdrawn Demand Deposit Accounts OverdrawnDemandDepositAccounts	90400000	USD
CY2018Q4	ntrs	Overdrawn Demand Deposit Accounts OverdrawnDemandDepositAccounts	152500000	USD
CY2019Q4	us-gaap	Direct Financing Lease Lease Receivable DirectFinancingLeaseLeaseReceivable	1500000	USD
CY2018Q4	us-gaap	Direct Financing Lease Lease Receivable DirectFinancingLeaseLeaseReceivable	9800000	USD
CY2019Q4	us-gaap	Direct Financing Lease Unguaranteed Residual Asset DirectFinancingLeaseUnguaranteedResidualAsset	21300000	USD
CY2018Q4	us-gaap	Direct Financing Lease Unguaranteed Residual Asset DirectFinancingLeaseUnguaranteedResidualAsset	23800000	USD
CY2019Q4	ntrs	Direct Financing Lease Initial Direct Costs DirectFinancingLeaseInitialDirectCosts	200000	USD
CY2018Q4	us-gaap	Capital Leases Net Investment In Direct Financing Leases Initial Direct Costs CapitalLeasesNetInvestmentInDirectFinancingLeasesInitialDirectCosts	300000	USD
CY2019Q4	us-gaap	Direct Financing Lease Deferred Selling Profit DirectFinancingLeaseDeferredSellingProfit	0	USD
CY2018Q4	us-gaap	Direct Financing Lease Deferred Selling Profit DirectFinancingLeaseDeferredSellingProfit	0	USD
CY2019Q4	us-gaap	Direct Financing Lease Net Investment In Lease DirectFinancingLeaseNetInvestmentInLease	23000000.0	USD
CY2018Q4	us-gaap	Direct Financing Lease Net Investment In Lease DirectFinancingLeaseNetInvestmentInLease	33900000	USD
CY2019Q4	us-gaap	Leveraged Leases Net Investment In Leveraged Leases Disclosure Rental Receivables Net LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureRentalReceivablesNet	19100000	USD
CY2018Q4	us-gaap	Leveraged Leases Net Investment In Leveraged Leases Disclosure Rental Receivables Net LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureRentalReceivablesNet	33900000	USD
CY2019Q4	us-gaap	Leveraged Leases Net Investment In Leveraged Leases Disclosure Residual Value Of Leased Assets LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureResidualValueOfLeasedAssets	33100000	USD
CY2018Q4	us-gaap	Leveraged Leases Net Investment In Leveraged Leases Disclosure Residual Value Of Leased Assets LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureResidualValueOfLeasedAssets	33300000	USD
CY2019Q4	us-gaap	Leveraged Leases Net Investment In Leveraged Leases Disclosure Deferred Income LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureDeferredIncome	9600000	USD
CY2018Q4	us-gaap	Leveraged Leases Net Investment In Leveraged Leases Disclosure Deferred Income LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureDeferredIncome	10400000	USD
CY2019Q4	us-gaap	Leveraged Leases Net Investment In Leveraged Leases Disclosure Investment In Leveraged Leases Net LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureInvestmentInLeveragedLeasesNet	42600000	USD
CY2018Q4	us-gaap	Leveraged Leases Net Investment In Leveraged Leases Disclosure Investment In Leveraged Leases Net LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureInvestmentInLeveragedLeasesNet	56800000	USD
CY2019Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	65600000	USD
CY2018Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	90700000	USD
CY2019Q4	us-gaap	Finance Lease Liability Payments Due Next Twelve Months FinanceLeaseLiabilityPaymentsDueNextTwelveMonths	3700000	USD
CY2019Q4	us-gaap	Finance Lease Liability Payments Due Year Two FinanceLeaseLiabilityPaymentsDueYearTwo	2100000	USD
CY2019Q4	us-gaap	Finance Lease Liability Payments Due Year Three FinanceLeaseLiabilityPaymentsDueYearThree	0	USD
CY2019Q4	us-gaap	Finance Lease Liability Payments Due Year Four FinanceLeaseLiabilityPaymentsDueYearFour	0	USD
CY2019Q4	us-gaap	Finance Lease Liability Payments Due Year Five FinanceLeaseLiabilityPaymentsDueYearFive	0	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	31409600000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	32490000000.0	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	31409600000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	32490000000.0	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Recorded Investment ImpairedFinancingReceivableRecordedInvestment	92200000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Unpaid Principal Balance ImpairedFinancingReceivableUnpaidPrincipalBalance	123700000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	5000000.0	USD
CY2018Q4	us-gaap	Impaired Financing Receivable Recorded Investment ImpairedFinancingReceivableRecordedInvestment	116200000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable Unpaid Principal Balance ImpairedFinancingReceivableUnpaidPrincipalBalance	150600000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	7200000	USD
CY2019	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	120200000	USD
CY2019	us-gaap	Impaired Financing Receivable Interest Income Accrual Method ImpairedFinancingReceivableInterestIncomeAccrualMethod	2200000	USD
CY2018	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	124600000	USD
CY2018	us-gaap	Impaired Financing Receivable Interest Income Accrual Method ImpairedFinancingReceivableInterestIncomeAccrualMethod	2200000	USD
CY2019	ntrs	Loans And Leases Receivable Non Performing Loans Interest That Would Have Been Recognized LoansAndLeasesReceivableNonPerformingLoansInterestThatWouldHaveBeenRecognized	7300000	USD
CY2018	ntrs	Loans And Leases Receivable Non Performing Loans Interest That Would Have Been Recognized LoansAndLeasesReceivableNonPerformingLoansInterestThatWouldHaveBeenRecognized	8000000.0	USD
CY2017	ntrs	Loans And Leases Receivable Non Performing Loans Interest That Would Have Been Recognized LoansAndLeasesReceivableNonPerformingLoansInterestThatWouldHaveBeenRecognized	9100000	USD
CY2019Q4	ntrs	Loans And Leases Receivable Commitment To Lend LoansAndLeasesReceivableCommitmentToLend	9100000	USD
CY2018Q4	ntrs	Loans And Leases Receivable Commitment To Lend LoansAndLeasesReceivableCommitmentToLend	12600000	USD
CY2019Q2	us-gaap	Financing Receivable Modifications Recorded Investment FinancingReceivableModificationsRecordedInvestment	5800000	USD
CY2019Q4	us-gaap	Financing Receivable Modifications Recorded Investment FinancingReceivableModificationsRecordedInvestment	6100000	USD
CY2017Q4	us-gaap	Financing Receivable Modifications Recorded Investment FinancingReceivableModificationsRecordedInvestment	2100000	USD
CY2018Q1	us-gaap	Financing Receivable Modifications Recorded Investment FinancingReceivableModificationsRecordedInvestment	2400000	USD
CY2019Q4	us-gaap	Mortgage Loans In Process Of Foreclosure Amount MortgageLoansInProcessOfForeclosureAmount	18100000	USD
CY2018Q4	us-gaap	Mortgage Loans In Process Of Foreclosure Amount MortgageLoansInProcessOfForeclosureAmount	10900000	USD
CY2018Q4	ntrs	Loans And Leases Receivable Allowance For Losses LoansAndLeasesReceivableAllowanceForLosses	138200000	USD
CY2017Q4	ntrs	Loans And Leases Receivable Allowance For Losses LoansAndLeasesReceivableAllowanceForLosses	153800000	USD
CY2016Q4	ntrs	Loans And Leases Receivable Allowance For Losses LoansAndLeasesReceivableAllowanceForLosses	192000000.0	USD
CY2019	us-gaap	Allowance For Loan And Lease Losses Write Offs AllowanceForLoanAndLeaseLossesWriteOffs	6500000	USD
CY2018	us-gaap	Allowance For Loan And Lease Losses Write Offs AllowanceForLoanAndLeaseLossesWriteOffs	10100000	USD
CY2017	us-gaap	Allowance For Loan And Lease Losses Write Offs AllowanceForLoanAndLeaseLossesWriteOffs	21500000	USD
CY2019	us-gaap	Allowance For Loan And Lease Loss Recovery Of Bad Debts AllowanceForLoanAndLeaseLossRecoveryOfBadDebts	7200000	USD
CY2018	us-gaap	Allowance For Loan And Lease Loss Recovery Of Bad Debts AllowanceForLoanAndLeaseLossRecoveryOfBadDebts	9000000.0	USD
CY2017	us-gaap	Allowance For Loan And Lease Loss Recovery Of Bad Debts AllowanceForLoanAndLeaseLossRecoveryOfBadDebts	11300000	USD
CY2019	us-gaap	Allowance For Loan And Lease Losses Adjustments Net AllowanceForLoanAndLeaseLossesAdjustmentsNet	700000	USD
CY2018	us-gaap	Allowance For Loan And Lease Losses Adjustments Net AllowanceForLoanAndLeaseLossesAdjustmentsNet	-1100000	USD
CY2017	us-gaap	Allowance For Loan And Lease Losses Adjustments Net AllowanceForLoanAndLeaseLossesAdjustmentsNet	-10200000	USD
CY2019	ntrs	Provision For Recovery Of Loan And Lease Losses ProvisionForRecoveryOfLoanAndLeaseLosses	-14500000	USD
CY2018	ntrs	Provision For Recovery Of Loan And Lease Losses ProvisionForRecoveryOfLoanAndLeaseLosses	-14500000	USD
CY2017	ntrs	Provision For Recovery Of Loan And Lease Losses ProvisionForRecoveryOfLoanAndLeaseLosses	-28000000.0	USD
CY2019Q4	ntrs	Loans And Leases Receivable Allowance For Losses LoansAndLeasesReceivableAllowanceForLosses	124400000	USD
CY2018Q4	ntrs	Loans And Leases Receivable Allowance For Losses LoansAndLeasesReceivableAllowanceForLosses	138200000	USD
CY2017Q4	ntrs	Loans And Leases Receivable Allowance For Losses LoansAndLeasesReceivableAllowanceForLosses	153800000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	104500000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	112600000	USD
CY2017Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	131200000	USD
CY2019Q4	ntrs	Unfunded Commitments And Standby Letters Of Credit Allowance UnfundedCommitmentsAndStandbyLettersOfCreditAllowance	19900000	USD
CY2018Q4	ntrs	Unfunded Commitments And Standby Letters Of Credit Allowance UnfundedCommitmentsAndStandbyLettersOfCreditAllowance	25600000	USD
CY2017Q4	ntrs	Unfunded Commitments And Standby Letters Of Credit Allowance UnfundedCommitmentsAndStandbyLettersOfCreditAllowance	22600000	USD
CY2019Q4	ntrs	Loans And Leases Receivable Allowance For Losses LoansAndLeasesReceivableAllowanceForLosses	124400000	USD
CY2018Q4	ntrs	Loans And Leases Receivable Allowance For Losses LoansAndLeasesReceivableAllowanceForLosses	138200000	USD
CY2017Q4	ntrs	Loans And Leases Receivable Allowance For Losses LoansAndLeasesReceivableAllowanceForLosses	153800000	USD
CY2019Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	92200000	USD
CY2019Q4	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	31317400000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	31409600000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	5000000.0	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	99500000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	104500000	USD
CY2019Q4	ntrs	Unfunded Commitments And Standby Letters Of Credit Allowance UnfundedCommitmentsAndStandbyLettersOfCreditAllowance	19900000	USD
CY2019Q4	ntrs	Loans And Leases Receivable Allowance For Losses LoansAndLeasesReceivableAllowanceForLosses	124400000	USD
CY2018Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	116200000	USD
CY2018Q4	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	32373800000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	32490000000.0	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	7200000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	105400000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	112600000	USD
CY2018Q4	ntrs	Unfunded Commitments And Standby Letters Of Credit Allowance UnfundedCommitmentsAndStandbyLettersOfCreditAllowance	25600000	USD
CY2018Q4	ntrs	Loans And Leases Receivable Allowance For Losses LoansAndLeasesReceivableAllowanceForLosses	138200000	USD
CY2019Q4	ntrs	Credit Risk To Banks Non Interest Bearing Balances Held At Banks CreditRiskToBanksNonInterestBearingBalancesHeldAtBanks	4900000000	USD
CY2019Q4	us-gaap	Federal Funds Sold And Securities Purchased Under Agreements To Resell FederalFundsSoldAndSecuritiesPurchasedUnderAgreementsToResell	712800000	USD
CY2019Q4	ntrs	Credit Risk To Banks CreditRiskToBanks	4300000000	USD
CY2018Q4	ntrs	Credit Risk To Banks Non Interest Bearing Balances Held At Banks CreditRiskToBanksNonInterestBearingBalancesHeldAtBanks	4300000000	USD
CY2018Q4	us-gaap	Federal Funds Sold And Securities Purchased Under Agreements To Resell FederalFundsSoldAndSecuritiesPurchasedUnderAgreementsToResell	1200000000	USD
CY2018Q4	ntrs	Credit Risk To Banks CreditRiskToBanks	4500000000	USD
CY2019Q4	ntrs	Loans And Leases Receivable Residential Real Estate LoansAndLeasesReceivableResidentialRealEstate	6000000000.0	USD
CY2019Q4	ntrs	Residential Real Estate Loans Percentage Of Total Us Loansand Leases ResidentialRealEstateLoansPercentageOfTotalUSLoansandLeases	0.20
CY2018Q4	ntrs	Loans And Leases Receivable Residential Real Estate LoansAndLeasesReceivableResidentialRealEstate	6500000000	USD
CY2018Q4	ntrs	Residential Real Estate Loans Percentage Of Total Us Loansand Leases ResidentialRealEstateLoansPercentageOfTotalUSLoansandLeases	0.22
CY2019Q4	ntrs	Lower Limit Of Generally Required Loan To Collateral Value For Residential Real Estate Loans LowerLimitOfGenerallyRequiredLoanToCollateralValueForResidentialRealEstateLoans	0.65
CY2019Q4	ntrs	Upper Limit Of Generally Required Loan To Collateral Value For Residential Real Estate Loans UpperLimitOfGenerallyRequiredLoanToCollateralValueForResidentialRealEstateLoans	0.80
CY2019Q4	ntrs	Loans And Leases Receivable Residential Real Estate LoansAndLeasesReceivableResidentialRealEstate	6000000000.0	USD
CY2019Q4	ntrs	Commitments To Extend Credit CommitmentsToExtendCredit	714200000	USD
CY2018Q4	ntrs	Commitments To Extend Credit CommitmentsToExtendCredit	824000000.0	USD
CY2019Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	1467400000	USD
CY2019Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	984100000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	483300000	USD
CY2018Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	1317000000.0	USD
CY2018Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	888800000	USD
CY2018Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	428200000	USD
CY2019	us-gaap	Depreciation Nonproduction DepreciationNonproduction	103200000	USD
CY2018	us-gaap	Depreciation Nonproduction DepreciationNonproduction	108600000	USD
CY2017	us-gaap	Depreciation Nonproduction DepreciationNonproduction	101200000	USD
CY2019	us-gaap	Operating Lease Cost OperatingLeaseCost	102200000	USD
CY2019	us-gaap	Variable Lease Cost VariableLeaseCost	38700000	USD
CY2019	us-gaap	Sublease Income SubleaseIncome	6600000	USD
CY2019	us-gaap	Lease Cost LeaseCost	134300000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	101300000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	85800000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	78500000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	70500000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	59600000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	300000000.0	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	695700000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	92600000	USD
CY2019Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	603100000	USD
CY2019Q4	ntrs	Lessee Operating Lease Lease Notyet Commenced Liability LesseeOperatingLeaseLeaseNotyetCommencedLiability	40100000	USD
CY2019Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	491600000	USD
CY2019Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	603100000	USD
CY2019Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P9Y2M12D
CY2019Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.030
CY2019	us-gaap	Operating Lease Payments OperatingLeasePayments	101200000	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	108300000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due Current OperatingLeasesFutureMinimumPaymentsDueCurrent	98800000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due In Two Years OperatingLeasesFutureMinimumPaymentsDueInTwoYears	97800000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due In Three Years OperatingLeasesFutureMinimumPaymentsDueInThreeYears	85900000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due In Four Years OperatingLeasesFutureMinimumPaymentsDueInFourYears	77200000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due In Five Years OperatingLeasesFutureMinimumPaymentsDueInFiveYears	67700000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due Thereafter OperatingLeasesFutureMinimumPaymentsDueThereafter	335700000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due OperatingLeasesFutureMinimumPaymentsDue	763100000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due Future Minimum Sublease Rentals OperatingLeasesFutureMinimumPaymentsDueFutureMinimumSubleaseRentals	23400000	USD
CY2018Q4	ntrs	Operating Leases Future Minimum Payments Due Net Of Future Minimum Sublease Rentals OperatingLeasesFutureMinimumPaymentsDueNetOfFutureMinimumSubleaseRentals	739700000	USD
CY2018	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	79000000.0	USD
CY2017	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	76700000	USD
CY2016	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	76100000	USD
CY2017Q4	us-gaap	Goodwill Goodwill	605600000	USD
CY2018	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	71400000	USD
CY2018	us-gaap	Goodwill Foreign Currency Translation Gain Loss GoodwillForeignCurrencyTranslationGainLoss	-7700000	USD
CY2018Q4	us-gaap	Goodwill Goodwill	669300000	USD
CY2019	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	23500000	USD
CY2019	us-gaap	Goodwill Foreign Currency Translation Gain Loss GoodwillForeignCurrencyTranslationGainLoss	4000000.0	USD
CY2019Q4	us-gaap	Goodwill Goodwill	696800000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	207200000	USD
CY2018Q4	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	211100000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	86600000	USD
CY2018Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	72500000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	120600000	USD
CY2018Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	138600000	USD
CY2019Q4	ntrs	Contractual Maturities Time Deposits100000 Or More Next Twelve Months ContractualMaturitiesTimeDeposits100000OrMoreNextTwelveMonths	1692500000	USD
CY2019Q4	ntrs	Contractual Maturities Time Deposits100000 Or More Year Two ContractualMaturitiesTimeDeposits100000OrMoreYearTwo	196600000	USD
CY2019Q4	ntrs	Contractual Maturities Time Deposits100000 Or More Year Three ContractualMaturitiesTimeDeposits100000OrMoreYearThree	7400000	USD
CY2019Q4	ntrs	Contractual Maturities Time Deposits100000 Or More Year Four ContractualMaturitiesTimeDeposits100000OrMoreYearFour	3800000	USD
CY2019Q4	ntrs	Contractual Maturities Time Deposits100000 Or More Year Five ContractualMaturitiesTimeDeposits100000OrMoreYearFive	4200000	USD
CY2019Q4	ntrs	Contractual Maturities Time Deposits100000 Or More After Year Five ContractualMaturitiesTimeDeposits100000OrMoreAfterYearFive	900000	USD
CY2019Q4	us-gaap	Time Deposits100000 Or More TimeDeposits100000OrMore	1905400000	USD
CY2018Q4	us-gaap	Time Deposits100000 Or More TimeDeposits100000OrMore	1300000000	USD
CY2018Q4	us-gaap	Interest Bearing Domestic Deposit Certificates Of Deposits InterestBearingDomesticDepositCertificatesOfDeposits	580900000	USD
CY2018Q4	us-gaap	Deposits Foreign DepositsForeign	758600000	USD
CY2019Q4	us-gaap	Senior Notes SeniorNotes	2573000000.0	USD
CY2018Q4	us-gaap	Senior Notes SeniorNotes	2011300000	USD
CY2019Q4	ntrs	Long Term Debt Qualifying As Risk Based Capital LongTermDebtQualifyingAsRiskBasedCapital	1099500000	USD
CY2018Q4	ntrs	Long Term Debt Qualifying As Risk Based Capital LongTermDebtQualifyingAsRiskBasedCapital	1099500000	USD
CY2019	us-gaap	Debt Instrument Redemption Price Percentage DebtInstrumentRedemptionPricePercentage	1
CY2019Q4	ntrs	Percentageof Securities Eligiblefor Tier2 Capital Treatment PercentageofSecuritiesEligibleforTier2CapitalTreatment	0.30
CY2019Q4	ntrs	Securities Eligiblefor Tier2 Capital Treatment Decline Rate SecuritiesEligibleforTier2CapitalTreatmentDeclineRate	0.10
CY2019Q4	ntrs	Debt Instrument Liquidation Amount Per Share DebtInstrumentLiquidationAmountPerShare	1000
CY2019Q4	ntrs	Trust Preferred Securities TrustPreferredSecurities	277700000	USD
CY2018Q4	ntrs	Trust Preferred Securities TrustPreferredSecurities	277600000	USD
CY2019Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	10000000	shares
CY2018Q3	us-gaap	Stock Repurchase Program Number Of Shares Authorized To Be Repurchased StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased	25000000.0	shares
CY2019	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	93.40
CY2018	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	102.69
CY2017	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	90.25
CY2018Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	219012050	shares
CY2017Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	226126674	shares
CY2016Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	228605485	shares
CY2019	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	1688931	shares
CY2018	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	1310778	shares
CY2017	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	1320129	shares
CY2019	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	786931	shares
CY2018	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	575662	shares
CY2017	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	1997362	shares
CY2019	us-gaap	Stock Redeemed Or Called During Period Shares StockRedeemedOrCalledDuringPeriodShares	11778866	shares
CY2018	us-gaap	Stock Redeemed Or Called During Period Shares StockRedeemedOrCalledDuringPeriodShares	9001064	shares
CY2017	us-gaap	Stock Redeemed Or Called During Period Shares StockRedeemedOrCalledDuringPeriodShares	5796302	shares
CY2019Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	209709046	shares
CY2018Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	219012050	shares
CY2017Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	226126674	shares
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-44300000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-14100000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	259000000.0	USD
CY2019	us-gaap	Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	347900000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Tax Portion Attributable To Parent1 OtherComprehensiveIncomeLossTaxPortionAttributableToParent1	88900000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	259000000.0	USD
CY2018	us-gaap	Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	11600000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Tax Portion Attributable To Parent1 OtherComprehensiveIncomeLossTaxPortionAttributableToParent1	25700000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-14100000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	-156700000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Tax Portion Attributable To Parent1 OtherComprehensiveIncomeLossTaxPortionAttributableToParent1	-112400000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-44300000	USD
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	214525547	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	223148335	shares
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	228257664	shares
CY2019	us-gaap	Net Income Loss NetIncomeLoss	1492200000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	1556400000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	1199000000.0	USD
CY2019	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	46400000	USD
CY2018	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	46400000	USD
CY2017	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	49800000	USD
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	1445800000	USD
CY2018	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	1510000000.0	USD
CY2017	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	1149200000	USD
CY2019	us-gaap	Undistributed Earnings Loss Allocated To Participating Securities Basic UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic	16900000	USD
CY2018	us-gaap	Undistributed Earnings Loss Allocated To Participating Securities Basic UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic	20100000	USD
CY2017	us-gaap	Undistributed Earnings Loss Allocated To Participating Securities Basic UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic	18800000	USD
CY2019	ntrs	Net Income Loss Allocated To Common Stockholders Basic NetIncomeLossAllocatedToCommonStockholdersBasic	1428900000	USD
CY2018	ntrs	Net Income Loss Allocated To Common Stockholders Basic NetIncomeLossAllocatedToCommonStockholdersBasic	1489900000	USD
CY2017	ntrs	Net Income Loss Allocated To Common Stockholders Basic NetIncomeLossAllocatedToCommonStockholdersBasic	1130400000	USD
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	6.66
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	6.68
CY2017	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.95
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	214525547	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	223148335	shares
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	228257664	shares
CY2019	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	1075602	shares
CY2018	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	1339991	shares
CY2017	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	1396737	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	215601149	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	224488326	shares
CY2017	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	229654401	shares
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	1428900000	USD
CY2018	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	1490000000.0	USD
CY2017	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	1130500000	USD
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	6.63
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	6.64
CY2017	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.92
CY2019	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
CY2017	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	115491	shares
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3852100000	USD
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3753700000	USD
CY2019	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	250900000	USD
CY2018	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	307200000	USD
CY2019	ntrs	Treasury Management Fees TreasuryManagementFees	44500000	USD
CY2018	ntrs	Treasury Management Fees TreasuryManagementFees	51800000	USD
CY2019	ntrs	Security Commissionsand Trading Income SecurityCommissionsandTradingIncome	103600000	USD
CY2018	ntrs	Security Commissionsand Trading Income SecurityCommissionsandTradingIncome	98300000	USD
CY2019	us-gaap	Other Operating Income OtherOperatingIncome	145500000	USD
CY2018	us-gaap	Other Operating Income OtherOperatingIncome	127500000	USD
CY2019	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1400000	USD
CY2018	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1000000.0	USD
CY2019	ntrs	Other Noninterest Income OtherNoninterestIncome	543100000	USD
CY2018	ntrs	Other Noninterest Income OtherNoninterestIncome	583800000	USD
CY2019	us-gaap	Noninterest Income NoninterestIncome	4395200000	USD
CY2018	us-gaap	Noninterest Income NoninterestIncome	4337500000	USD
CY2019	ntrs	Security Commissionsand Trading Income SecurityCommissionsandTradingIncome	103600000	USD
CY2019	us-gaap	Other Operating Income OtherOperatingIncome	145500000	USD
CY2018	ntrs	Security Commissionsand Trading Income SecurityCommissionsandTradingIncome	98300000	USD
CY2018	us-gaap	Other Operating Income OtherOperatingIncome	127500000	USD
CY2019Q4	us-gaap	Contract With Customer Asset Net ContractWithCustomerAssetNet	903000000.0	USD
CY2018Q4	us-gaap	Contract With Customer Asset Net ContractWithCustomerAssetNet	832600000	USD
CY2019	us-gaap	Interest And Fee Income Loans And Leases InterestAndFeeIncomeLoansAndLeases	1153400000	USD
CY2018	us-gaap	Interest And Fee Income Loans And Leases InterestAndFeeIncomeLoansAndLeases	1098800000	USD
CY2017	us-gaap	Interest And Fee Income Loans And Leases InterestAndFeeIncomeLoansAndLeases	919100000	USD
CY2019	us-gaap	Interest Income Securities Taxable InterestIncomeSecuritiesTaxable	1070700000	USD
CY2018	us-gaap	Interest Income Securities Taxable InterestIncomeSecuritiesTaxable	905200000	USD
CY2017	us-gaap	Interest Income Securities Taxable InterestIncomeSecuritiesTaxable	594100000	USD
CY2019	us-gaap	Interest Income Securities Tax Exempt InterestIncomeSecuritiesTaxExempt	3800000	USD
CY2018	us-gaap	Interest Income Securities Tax Exempt InterestIncomeSecuritiesTaxExempt	7000000.0	USD
CY2017	us-gaap	Interest Income Securities Tax Exempt InterestIncomeSecuritiesTaxExempt	9800000	USD
CY2019	us-gaap	Interest Income Deposits With Financial Institutions InterestIncomeDepositsWithFinancialInstitutions	72400000	USD
CY2018	us-gaap	Interest Income Deposits With Financial Institutions InterestIncomeDepositsWithFinancialInstitutions	70000000.0	USD
CY2017	us-gaap	Interest Income Deposits With Financial Institutions InterestIncomeDepositsWithFinancialInstitutions	63800000	USD
CY2019	ntrs	Interest Income Federal Reserve Deposits And Other InterestIncomeFederalReserveDepositsAndOther	199600000	USD
CY2018	ntrs	Interest Income Federal Reserve Deposits And Other InterestIncomeFederalReserveDepositsAndOther	240400000	USD
CY2017	ntrs	Interest Income Federal Reserve Deposits And Other InterestIncomeFederalReserveDepositsAndOther	182600000	USD
CY2019	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	2499900000	USD
CY2018	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	2321400000	USD
CY2017	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	1769400000	USD
CY2019	us-gaap	Interest Expense Deposits InterestExpenseDeposits	488900000	USD
CY2018	us-gaap	Interest Expense Deposits InterestExpenseDeposits	384600000	USD
CY2017	us-gaap	Interest Expense Deposits InterestExpenseDeposits	182100000	USD
CY2019	us-gaap	Interest Expense Federal Funds Purchased InterestExpenseFederalFundsPurchased	25900000	USD
CY2018	us-gaap	Interest Expense Federal Funds Purchased InterestExpenseFederalFundsPurchased	50300000	USD
CY2017	us-gaap	Interest Expense Federal Funds Purchased InterestExpenseFederalFundsPurchased	10400000	USD
CY2019	us-gaap	Interest Expense Securities Sold Under Agreements To Repurchase InterestExpenseSecuritiesSoldUnderAgreementsToRepurchase	6400000	USD
CY2018	us-gaap	Interest Expense Securities Sold Under Agreements To Repurchase InterestExpenseSecuritiesSoldUnderAgreementsToRepurchase	7800000	USD
CY2017	us-gaap	Interest Expense Securities Sold Under Agreements To Repurchase InterestExpenseSecuritiesSoldUnderAgreementsToRepurchase	6000000.0	USD
CY2019	us-gaap	Interest Expense Other Short Term Borrowings InterestExpenseOtherShortTermBorrowings	181700000	USD
CY2018	us-gaap	Interest Expense Other Short Term Borrowings InterestExpenseOtherShortTermBorrowings	150100000	USD
CY2017	us-gaap	Interest Expense Other Short Term Borrowings InterestExpenseOtherShortTermBorrowings	50700000	USD
CY2019	ntrs	Interest Expense Senior Notes InterestExpenseSeniorNotes	72600000	USD
CY2018	ntrs	Interest Expense Senior Notes InterestExpenseSeniorNotes	53400000	USD
CY2017	ntrs	Interest Expense Senior Notes InterestExpenseSeniorNotes	46900000	USD
CY2019	us-gaap	Interest Expense Other Long Term Debt InterestExpenseOtherLongTermDebt	38300000	USD
CY2018	us-gaap	Interest Expense Other Long Term Debt InterestExpenseOtherLongTermDebt	45000000.0	USD
CY2017	us-gaap	Interest Expense Other Long Term Debt InterestExpenseOtherLongTermDebt	39200000	USD
CY2019	us-gaap	Interest Expense Junior Subordinated Debentures InterestExpenseJuniorSubordinatedDebentures	8200000	USD
CY2018	us-gaap	Interest Expense Junior Subordinated Debentures InterestExpenseJuniorSubordinatedDebentures	7500000	USD
CY2017	us-gaap	Interest Expense Junior Subordinated Debentures InterestExpenseJuniorSubordinatedDebentures	4900000	USD
CY2019	us-gaap	Interest Expense InterestExpense	822000000.0	USD
CY2018	us-gaap	Interest Expense InterestExpense	698700000	USD
CY2017	us-gaap	Interest Expense InterestExpense	340200000	USD
CY2019	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	1677900000	USD
CY2018	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	1622700000	USD
CY2017	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	1429200000	USD
CY2019	us-gaap	Other Operating Income OtherOperatingIncome	145500000	USD
CY2018	us-gaap	Other Operating Income OtherOperatingIncome	127500000	USD
CY2017	us-gaap	Other Operating Income OtherOperatingIncome	157500000	USD
CY2019	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	104200000	USD
CY2018	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	98300000	USD
CY2017	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	95400000	USD
CY2019	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	9900000	USD
CY2018	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	27400000	USD
CY2017	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	34700000	USD
CY2019	us-gaap	Other Labor Related Expenses OtherLaborRelatedExpenses	42800000	USD
CY2018	us-gaap	Other Labor Related Expenses OtherLaborRelatedExpenses	33600000	USD
CY2017	us-gaap	Other Labor Related Expenses OtherLaborRelatedExpenses	42800000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	16600000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	17400000	USD
CY2017	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	11400000	USD
CY2019	ntrs	Noninterest Expense Other NoninterestExpenseOther	156300000	USD
CY2018	ntrs	Noninterest Expense Other NoninterestExpenseOther	153900000	USD
CY2017	ntrs	Noninterest Expense Other NoninterestExpenseOther	147300000	USD
CY2019	us-gaap	Other Noninterest Expense OtherNoninterestExpense	329800000	USD
CY2018	us-gaap	Other Noninterest Expense OtherNoninterestExpense	330600000	USD
CY2017	us-gaap	Other Noninterest Expense OtherNoninterestExpense	331600000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2018	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2017	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.350
CY2019	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	408300000	USD
CY2018	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	411100000	USD
CY2017	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	571900000	USD
CY2019	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	11500000	USD
CY2018	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	6900000	USD
CY2017	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	9600000	USD
CY2019	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	4600000	USD
CY2018	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	-7300000	USD
CY2017	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	-50000000.0	USD
CY2019	ntrs	Income Tax Reconciliation Leveraged Lease Adjustments IncomeTaxReconciliationLeveragedLeaseAdjustments	-17500000	USD
CY2018	ntrs	Income Tax Reconciliation Leveraged Lease Adjustments IncomeTaxReconciliationLeveragedLeaseAdjustments	-16800000	USD
CY2017	ntrs	Income Tax Reconciliation Leveraged Lease Adjustments IncomeTaxReconciliationLeveragedLeaseAdjustments	-31600000	USD
CY2019	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	55000000.0	USD
CY2018	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	66300000	USD
CY2017	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	40700000	USD
CY2019	ntrs	Effective Income Tax Rate Reconciliation Effectof Tax Cutsand Jobs Actof2017 Amount EffectiveIncomeTaxRateReconciliationEffectofTaxCutsandJobsActof2017Amount	0	USD
CY2018	ntrs	Effective Income Tax Rate Reconciliation Effectof Tax Cutsand Jobs Actof2017 Amount EffectiveIncomeTaxRateReconciliationEffectofTaxCutsandJobsActof2017Amount	4800000	USD
CY2017	ntrs	Effective Income Tax Rate Reconciliation Effectof Tax Cutsand Jobs Actof2017 Amount EffectiveIncomeTaxRateReconciliationEffectofTaxCutsandJobsActof2017Amount	53100000	USD
CY2019	ntrs	Effective Income Tax Rate Reconciliation Effectof Changein Accounting Method Amount EffectiveIncomeTaxRateReconciliationEffectofChangeinAccountingMethodAmount	0	USD
CY2018	ntrs	Effective Income Tax Rate Reconciliation Effectof Changein Accounting Method Amount EffectiveIncomeTaxRateReconciliationEffectofChangeinAccountingMethodAmount	24400000	USD
CY2017	ntrs	Effective Income Tax Rate Reconciliation Effectof Changein Accounting Method Amount EffectiveIncomeTaxRateReconciliationEffectofChangeinAccountingMethodAmount	0	USD
CY2019	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	29500000	USD
CY2018	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	-800000	USD
CY2017	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	300000	USD
CY2019	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-16500000	USD
CY2018	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-15000000.0	USD
CY2017	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-33700000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	451900000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	401400000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	434900000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	451900000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	401400000	USD
CY2019	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.232
CY2018	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.205
CY2017	ntrs	Effective Income Tax Rate Reconciliation Effectof Tax Cutsand Jobs Actof2017 Amount EffectiveIncomeTaxRateReconciliationEffectofTaxCutsandJobsActof2017Amount	53100000	USD
CY2018	us-gaap	Tax Cuts And Jobs Act Of2017 Transition Tax For Accumulated Foreign Earnings Income Tax Expense TaxCutsAndJobsActOf2017TransitionTaxForAccumulatedForeignEarningsIncomeTaxExpense	-16800000	USD
CY2017	us-gaap	Tax Cuts And Jobs Act Of2017 Incomplete Accounting Transition Tax For Accumulated Foreign Earnings Provisional Income Tax Expense TaxCutsAndJobsActOf2017IncompleteAccountingTransitionTaxForAccumulatedForeignEarningsProvisionalIncomeTaxExpense	150000000.0	USD
CY2018	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Deferred Tax Liability Income Tax Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateDeferredTaxLiabilityIncomeTaxBenefit	-12700000	USD
CY2017	us-gaap	Tax Cuts And Jobs Act Of2017 Incomplete Accounting Change In Tax Rate Deferred Tax Liability Provisional Income Tax Benefit TaxCutsAndJobsActOf2017IncompleteAccountingChangeInTaxRateDeferredTaxLiabilityProvisionalIncomeTaxBenefit	210000000.0	USD
CY2018	us-gaap	Tax Cuts And Jobs Act Of2017 Measurement Period Adjustment Income Tax Expense Benefit TaxCutsAndJobsActOf2017MeasurementPeriodAdjustmentIncomeTaxExpenseBenefit	-700000	USD
CY2017	us-gaap	Tax Cuts And Jobs Act Of2017 Measurement Period Adjustment Income Tax Expense Benefit TaxCutsAndJobsActOf2017MeasurementPeriodAdjustmentIncomeTaxExpenseBenefit	6900000	USD
CY2018	us-gaap	Tax Cuts And Jobs Act Of2017 Income Tax Expense Benefit TaxCutsAndJobsActOf2017IncomeTaxExpenseBenefit	-4800000	USD
CY2017	us-gaap	Tax Cuts And Jobs Act Of2017 Incomplete Accounting Change In Tax Rate Provisional Income Tax Expense Benefit TaxCutsAndJobsActOf2017IncompleteAccountingChangeInTaxRateProvisionalIncomeTaxExpenseBenefit	-53100000	USD
CY2018	us-gaap	Tax Cuts And Jobs Act Of2017 Transition Tax For Accumulated Foreign Earnings Income Tax Expense TaxCutsAndJobsActOf2017TransitionTaxForAccumulatedForeignEarningsIncomeTaxExpense	-16800000	USD
CY2018	us-gaap	Tax Cuts And Jobs Act Of2017 Change In Tax Rate Deferred Tax Liability Income Tax Benefit TaxCutsAndJobsActOf2017ChangeInTaxRateDeferredTaxLiabilityIncomeTaxBenefit	-12700000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	25300000	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	21900000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	22700000	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	19800000	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	21900000	USD
CY2017Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	27700000	USD
CY2016Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	17200000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	900000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	500000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	9900000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	4000000.0	USD
CY2018	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	1700000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	6200000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	1500000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	7800000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	5400000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	0	USD
CY2018	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	200000	USD
CY2017	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	200000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	25300000	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	21900000	USD
CY2017Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	27700000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Period Increase Decrease UnrecognizedTaxBenefitsPeriodIncreaseDecrease	-3400000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	25300000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Period Increase Decrease UnrecognizedTaxBenefitsPeriodIncreaseDecrease	5800000	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	21900000	USD
CY2019	us-gaap	Income Tax Examination Penalties And Interest Expense IncomeTaxExaminationPenaltiesAndInterestExpense	1300000	USD
CY2018	us-gaap	Income Tax Examination Penalties And Interest Expense IncomeTaxExaminationPenaltiesAndInterestExpense	300000	USD
CY2017	us-gaap	Income Tax Examination Penalties And Interest Expense IncomeTaxExaminationPenaltiesAndInterestExpense	100000	USD
CY2019Q4	us-gaap	Income Tax Examination Penalties And Interest Accrued IncomeTaxExaminationPenaltiesAndInterestAccrued	8400000	USD
CY2018Q4	us-gaap	Income Tax Examination Penalties And Interest Accrued IncomeTaxExaminationPenaltiesAndInterestAccrued	9200000	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	216400000	USD
CY2018	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	132800000	USD
CY2017	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	347300000	USD
CY2019	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	50700000	USD
CY2018	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	95400000	USD
CY2017	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	38300000	USD
CY2019	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	150500000	USD
CY2018	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	162700000	USD
CY2017	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	125400000	USD
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	417600000	USD
CY2018	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	390900000	USD
CY2017	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	511000000.0	USD
CY2019	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	16500000	USD
CY2018	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	33800000	USD
CY2017	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-96400000	USD
CY2019	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	16500000	USD
CY2018	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-13800000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	434900000	USD
CY2017	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	24600000	USD
CY2019	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	1300000	USD
CY2018	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-9500000	USD
CY2017	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-4300000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	34300000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	10500000	USD
CY2017	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-76100000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	451900000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	401400000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	88900000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	25700000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	-112400000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	36900000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	43300000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Deferred Expense Capitalized Software DeferredTaxLiabilitiesDeferredExpenseCapitalizedSoftware	249400000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Deferred Expense Capitalized Software DeferredTaxLiabilitiesDeferredExpenseCapitalizedSoftware	193200000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	99800000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	129500000	USD
CY2019Q4	ntrs	Deferred Tax Liabilities Compensation And Benefits DeferredTaxLiabilitiesCompensationAndBenefits	8300000	USD
CY2018Q4	ntrs	Deferred Tax Liabilities Compensation And Benefits DeferredTaxLiabilitiesCompensationAndBenefits	10900000	USD
CY2019Q4	ntrs	Deferred Tax Liabilities State Taxes DeferredTaxLiabilitiesStateTaxes	66400000	USD
CY2018Q4	ntrs	Deferred Tax Liabilities State Taxes DeferredTaxLiabilitiesStateTaxes	58900000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	206700000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	114500000	USD
CY2019Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	667500000	USD
CY2018Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	550300000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Provision For Loan Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses	26100000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Provision For Loan Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses	29000000.0	USD
CY2019Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	147000000.0	USD
CY2018Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	120600000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	173100000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	149600000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	29800000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	300000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	143300000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	149300000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	524200000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	401000000.0	USD
CY2019	us-gaap	Defined Benefit Plan Actuarial Gain Loss DefinedBenefitPlanActuarialGainLoss	-256200000	USD
CY2018	us-gaap	Defined Benefit Plan Actuarial Gain Loss DefinedBenefitPlanActuarialGainLoss	131400000	USD
CY2019	ntrs	Number Of Investments Held In Diversified Portfolios NumberOfInvestmentsHeldInDiversifiedPortfolios	1	Investment
CY2019Q4	us-gaap	Derivative Number Of Instruments Held DerivativeNumberOfInstrumentsHeld	5	derivative_instrument
CY2018Q4	us-gaap	Derivative Number Of Instruments Held DerivativeNumberOfInstrumentsHeld	4	derivative_instrument
CY2019	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets	0.0525
CY2019	ntrs	Defined Benefit Plan Minimum Retirement Age DefinedBenefitPlanMinimumRetirementAge	55	Age
CY2019	ntrs	Defined Benefit Plan Minimum Service Term DefinedBenefitPlanMinimumServiceTerm	P15Y
CY2019	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	57600000	USD
CY2018	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	54400000	USD
CY2017	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	53400000	USD
CY2019	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	107900000	USD
CY2018	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	130900000	USD
CY2017	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	128000000.0	USD
CY2019	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	26700000	USD
CY2018	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	32500000	USD
CY2017	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	48700000	USD
CY2019Q4	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	77700000	USD
CY2019	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1	P2Y
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	0
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	0
CY2017	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	19.18
CY2019	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested In Period Fair Value1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1	6600000	USD
CY2018	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested In Period Fair Value1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1	8100000	USD
CY2017	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested In Period Fair Value1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1	7300000	USD
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	35400000	USD
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	28500000	USD
CY2017	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	74700000	USD
CY2019	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	44000000.0	USD
CY2018	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	32600000	USD
CY2019	ntrs	Employee Service Share Based Compensation Tax Benefit Realized From Exercise Of Stock Option EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOption	35200000	USD
CY2017	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	108000000.0	USD
CY2018	ntrs	Employee Service Share Based Compensation Tax Benefit Realized From Exercise Of Stock Option EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOption	27700000	USD
CY2017	ntrs	Employee Service Share Based Compensation Tax Benefit Realized From Exercise Of Stock Option EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOption	73100000	USD
CY2018Q4	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Nonvested Number Of Shares SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares	757738	shares
CY2018Q4	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Nonvested Weighted Average Grant Date Fair Value SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue	17.36
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod	0	shares
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	0
CY2019	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested Number Of Shares SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares	372799	shares
CY2019	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested Weighted Average Grant Date Fair Value SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue	17.26
CY2019	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Nonvested Options Forfeited Number Of Shares SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedNumberOfShares	0	shares
CY2019	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Nonvested Options Forfeited Weighted Average Grant Date Fair Value SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedWeightedAverageGrantDateFairValue	0
CY2019Q4	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Nonvested Number Of Shares SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares	384939	shares
CY2019Q4	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Nonvested Weighted Average Grant Date Fair Value SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue	17.45
CY2019Q4	us-gaap	Deferred Compensation Arrangement With Individual Cash Award Granted Amount DeferredCompensationArrangementWithIndividualCashAwardGrantedAmount	326100000	USD
CY2018Q4	us-gaap	Deferred Compensation Arrangement With Individual Cash Award Granted Amount DeferredCompensationArrangementWithIndividualCashAwardGrantedAmount	326500000	USD
CY2017Q4	us-gaap	Deferred Compensation Arrangement With Individual Cash Award Granted Amount DeferredCompensationArrangementWithIndividualCashAwardGrantedAmount	289800000	USD
CY2019	us-gaap	Loss Contingency Disclosures LossContingencyDisclosures	Contingent Liabilities<div style="line-height:120%;text-align:justify;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;font-weight:bold;">Legal Proceedings.</span><span style="font-family:inherit;font-size:10pt;"> In the normal course of business, the Corporation and its subsidiaries are routinely defendants in or parties to pending and threatened legal actions, and are subject to regulatory examinations, information-gathering requests, investigations, and proceedings, both formal and informal. In certain legal actions, claims for substantial monetary damages are asserted. In regulatory matters, claims for disgorgement, restitution, penalties and/or other remedial actions or sanctions may be sought. </span></div><div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Based on current knowledge, after consultation with legal counsel and after taking into account current accruals, management does not believe that losses, fines or penalties, if any, arising from pending litigation or threatened legal actions or regulatory matters either individually or in the aggregate, after giving effect to applicable reserves and insurance coverage will have a material adverse effect on the consolidated financial position or liquidity of the Corporation, although such matters could have a material adverse effect on the Corporation’s operating results for a particular period.</span></div><div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Under GAAP, (i) an event is “probable” if the “future event or events are likely to occur”; (ii) an event is “reasonably possible” if “the chance of the future event or events occurring is more than remote but less than likely”; and (iii) an event is “remote” if “the chance of the future event or events occurring is slight.”</span></div><div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">The outcome of litigation and regulatory matters is inherently difficult to predict and/or the range of loss often cannot be reasonably estimated, particularly for matters that (i) will be decided by a jury, (ii) are in early stages, (iii) involve uncertainty as to the likelihood of a class being certified or the ultimate size of the class, (iv) are subject to appeals or motions, (v) involve significant factual issues to be resolved, including with respect to the amount of damages, (vi) do not specify the amount of damages sought or (vii) seek very large damages based on novel and complex damage and liability legal theories. Accordingly, the Corporation cannot reasonably estimate the eventual outcome of these pending matters, the timing of their ultimate resolution or what the eventual loss, fines or penalties, if any, related to each pending matter will be.</span></div><div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">In accordance with applicable accounting guidance, the Corporation records accruals for litigation and regulatory matters when those matters present loss contingencies that are both probable and reasonably estimable. When loss contingencies are not both probable and reasonably estimable, the Corporation does not record accruals. </span><span style="font-family:inherit;font-size:10pt;"><span>No</span></span><span style="font-family:inherit;font-size:10pt;"> material accruals have been recorded for pending litigation or threatened legal actions or regulatory matters. </span></div><div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">For a limited number of matters for which a loss is reasonably possible in future periods, whether in excess of an accrued liability or where there is no accrued liability, the Corporation is able to estimate a range of possible loss. As of </span><span style="font-family:inherit;font-size:10pt;">December 31, 2019</span><span style="font-family:inherit;font-size:10pt;">, the Corporation has estimated the range of reasonably possible loss for these matters to be from </span><span style="font-family:inherit;font-size:10pt;"><span>zero</span></span><span style="font-family:inherit;font-size:10pt;"> to approximately </span><span style="font-family:inherit;font-size:10pt;"><span>$20 million</span></span><span style="font-family:inherit;font-size:10pt;"> in the aggregate. The Corporation’s estimate with respect to the aggregate range of reasonably possible loss is based upon currently available information and is subject to significant judgment and a variety of assumptions and known and unknown uncertainties. The matters underlying the estimated range will change from time to time, and actual results may vary significantly from the current estimate. </span></div><div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">In certain other pending matters, there may be a range of reasonably possible loss (including reasonably possible loss in excess of amounts accrued) that cannot be reasonably estimated for the reasons described above. Such matters are not included in the estimated range of reasonably possible loss discussed above. </span></div><div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">In 2015, Northern Trust Fiduciary Services (Guernsey) Limited (NTFS), an indirect subsidiary of the Corporation, was charged by a French investigating magistrate judge with complicity in estate tax fraud in connection with the administration of </span><span style="font-family:inherit;font-size:10pt;"><span>two</span></span><span style="font-family:inherit;font-size:10pt;"> trusts for which it serves as trustee. Charges also were brought against a number of other persons and entities related to this matter. In 2017, a French court found no estate tax fraud had occurred and NTFS and all other persons and entities charged were acquitted. The Public Prosecutor’s Office of France appealed the court decision and in June 2018 a French appellate court issued its opinion on the matter, acquitting all persons and entities charged, including NTFS. The Public Prosecutor’s Office of France has appealed the appellate court’s decision to the Cour de Cassation, the highest court in France. As trustee, NTFS provided no tax advice and had no involvement in the preparation or filing of the challenged estate tax filings.</span></div><div style="line-height:120%;text-align:justify;text-indent:48px;font-size:8pt;"><span style="font-family:inherit;font-size:8pt;font-weight:bold;"> </span></div><div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;font-weight:bold;">Visa Class B Common Shares.</span><span style="font-family:inherit;font-size:10pt;"> Northern Trust, as a member of Visa U.S.A. Inc. (Visa U.S.A.) and in connection with the 2007 restructuring of Visa U.S.A. and its affiliates and the 2008 initial public offering of Visa Inc. (Visa), received certain Visa Class B common shares. The Visa Class B common shares are subject to certain selling restrictions until the final resolution of certain litigation related to interchange fees involving Visa (the covered litigation), at which time the shares are convertible into Visa Class A common shares based on a conversion rate dependent upon the ultimate cost of resolving the covered litigation. On June 28, 2018, and September 27, 2019, Visa deposited an additional </span><span style="font-family:inherit;font-size:10pt;"><span>$600 million</span></span><span style="font-family:inherit;font-size:10pt;"> and </span><span style="font-family:inherit;font-size:10pt;"><span>$300 million</span></span><span style="font-family:inherit;font-size:10pt;">, respectively, into an escrow account previously established with respect to the covered litigation. As a result of the additional contributions to the escrow account, the rate at which Visa Class B common shares will convert into Visa Class A common shares was reduced. </span></div><div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">In September 2018, Visa reached a proposed class settlement agreement covering damage claims but not injunctive relief claims regarding the covered litigation. In December 2019, the district court granted final approval for the proposed class settlement agreement. Certain merchants have opted out of the class settlement and are pursuing claims separately, while other merchants have appealed the approval order granted by the district court. The ultimate resolution of the covered litigation, the timing for removal of the selling restrictions on the Visa Class B common shares and the rate at which such shares will ultimately convert into Visa Class A common shares are uncertain.</span></div><div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">In June 2016 and 2015, Northern Trust recorded a </span><span style="font-family:inherit;font-size:10pt;"><span>$123.1 million</span></span><span style="font-family:inherit;font-size:10pt;"> and </span><span style="font-family:inherit;font-size:10pt;"><span>$99.9 million</span></span><span style="font-family:inherit;font-size:10pt;"> net gain on the sale of </span><span style="font-family:inherit;font-size:10pt;"><span>1.1 million</span></span><span style="font-family:inherit;font-size:10pt;"> and </span><span style="font-family:inherit;font-size:10pt;"><span>1.0 million</span></span><span style="font-family:inherit;font-size:10pt;"> of its Visa Class B common shares, respectively. These sales do not affect Northern Trust’s risk related to the impact of the covered litigation on the rate at which such shares will ultimately convert into Visa Class A common shares. Northern Trust continued to hold approximately </span><span style="font-family:inherit;font-size:10pt;"><span>4.1 million</span></span><span style="font-family:inherit;font-size:10pt;"> Visa Class B common shares, which are recorded at their original cost basis of </span><span style="font-family:inherit;font-size:10pt;"><span>zero</span></span><span style="font-family:inherit;font-size:10pt;">, as of both </span><span style="font-family:inherit;font-size:10pt;">December 31, 2019</span><span style="font-family:inherit;font-size:10pt;"> and </span><span style="font-family:inherit;font-size:10pt;">2018</span><span style="font-family:inherit;font-size:10pt;">.</span></div><div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;"><br/></span></div><div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;font-weight:bold;">Clearing and Settlement Organizations.</span><span style="font-family:inherit;font-size:10pt;"> The Bank is a participating member of various cash, securities, and foreign exchange clearing and settlement organizations. It participates in these organizations on behalf of its clients and on its own behalf as a result of its own activities. A wide variety of cash and securities transactions are settled through these organizations, including those involving obligations of states and political subdivisions, asset-backed securities, commercial paper, dollar placements, and securities issued by the Government National Mortgage Association.</span></div><div style="line-height:120%;text-align:justify;text-indent:24px;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">As a result of its participation in cash, securities, and foreign exchange clearing and settlement organizations, the Bank could be responsible for a pro rata share of certain credit-related losses arising out of the clearing activities. The method in which such losses would be shared by the clearing members is stipulated in each clearing organization’s membership agreement. Credit exposure related to these agreements varies from day to day, primarily as a result of fluctuations in the volume of transactions cleared through the organizations. At </span><span style="font-family:inherit;font-size:10pt;">December 31, 2019</span><span style="font-family:inherit;font-size:10pt;"> and </span><span style="font-family:inherit;font-size:10pt;">2018</span><span style="font-family:inherit;font-size:10pt;">, we have not recorded any material liabilities under these arrangements. Controls related to these clearing transactions are closely monitored by management to protect the assets of Northern Trust and its clients.</span></div>
CY2019Q4	us-gaap	Loss Contingency Accrual At Carrying Value LossContingencyAccrualAtCarryingValue	0	USD
CY2019Q4	us-gaap	Derivative Notional Amount DerivativeNotionalAmount	310600700000	USD
CY2019Q4	us-gaap	Derivative Asset Fair Value Gross Asset Including Not Subject To Master Netting Arrangement DerivativeAssetFairValueGrossAssetIncludingNotSubjectToMasterNettingArrangement	3387700000	USD
CY2019Q4	us-gaap	Derivative Liability Fair Value Gross Liability Including Not Subject To Master Netting Arrangement DerivativeLiabilityFairValueGrossLiabilityIncludingNotSubjectToMasterNettingArrangement	3313000000.0	USD
CY2018Q4	us-gaap	Derivative Notional Amount DerivativeNotionalAmount	301494900000	USD
CY2018Q4	us-gaap	Derivative Asset Fair Value Gross Asset Including Not Subject To Master Netting Arrangement DerivativeAssetFairValueGrossAssetIncludingNotSubjectToMasterNettingArrangement	2563500000	USD
CY2018Q4	us-gaap	Derivative Liability Fair Value Gross Liability Including Not Subject To Master Netting Arrangement DerivativeLiabilityFairValueGrossLiabilityIncludingNotSubjectToMasterNettingArrangement	2388400000	USD
CY2019Q4	us-gaap	Derivative Asset Fair Value Gross Liability DerivativeAssetFairValueGrossLiability	2338000000.0	USD
CY2019Q4	us-gaap	Derivative Liability Fair Value Gross Asset DerivativeLiabilityFairValueGrossAsset	1618400000	USD
CY2018Q4	us-gaap	Derivative Asset Fair Value Gross Liability DerivativeAssetFairValueGrossLiability	1357100000	USD
CY2018Q4	us-gaap	Derivative Liability Fair Value Gross Asset DerivativeLiabilityFairValueGrossAsset	1796300000	USD
CY2019Q4	us-gaap	Derivative Assets DerivativeAssets	1049700000	USD
CY2019Q4	us-gaap	Derivative Liabilities DerivativeLiabilities	1694600000	USD
CY2018Q4	us-gaap	Derivative Assets DerivativeAssets	1206400000	USD
CY2018Q4	us-gaap	Derivative Liabilities DerivativeLiabilities	592100000	USD
CY2019Q4	us-gaap	Gain Loss On Discontinuation Of Cash Flow Hedge Due To Forecasted Transaction Probable Of Not Occurring Net GainLossOnDiscontinuationOfCashFlowHedgeDueToForecastedTransactionProbableOfNotOccurringNet	0	USD
CY2019	us-gaap	Maximum Length Of Time Foreign Currency Cash Flow Hedge MaximumLengthOfTimeForeignCurrencyCashFlowHedge	P23M
CY2019	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	2499900000	USD
CY2018	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	2321400000	USD
CY2017	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	1769400000	USD
CY2019	us-gaap	Interest Expense InterestExpense	822000000.0	USD
CY2018	us-gaap	Interest Expense InterestExpense	698700000	USD
CY2017	us-gaap	Interest Expense InterestExpense	340200000	USD
CY2019	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	145500000	USD
CY2018	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	127500000	USD
CY2017	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	157500000	USD
CY2019	us-gaap	Other Noninterest Expense OtherNoninterestExpense	329800000	USD
CY2018	us-gaap	Other Noninterest Expense OtherNoninterestExpense	330600000	USD
CY2017	us-gaap	Other Noninterest Expense OtherNoninterestExpense	331600000	USD
CY2019Q4	us-gaap	Hedged Asset Fair Value Hedge HedgedAssetFairValueHedge	2981000000.0	USD
CY2019Q4	us-gaap	Hedged Asset Fair Value Hedge Cumulative Increase Decrease HedgedAssetFairValueHedgeCumulativeIncreaseDecrease	3300000	USD
CY2018Q4	us-gaap	Hedged Asset Fair Value Hedge HedgedAssetFairValueHedge	3831600000	USD
CY2018Q4	us-gaap	Hedged Asset Fair Value Hedge Cumulative Increase Decrease HedgedAssetFairValueHedgeCumulativeIncreaseDecrease	99400000	USD
CY2019Q4	us-gaap	Hedged Liability Fair Value Hedge HedgedLiabilityFairValueHedge	1748500000	USD
CY2019Q4	us-gaap	Hedged Liability Fair Value Hedge Cumulative Increase Decrease HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease	126900000	USD
CY2018Q4	us-gaap	Hedged Liability Fair Value Hedge HedgedLiabilityFairValueHedge	1248800000	USD
CY2018Q4	us-gaap	Hedged Liability Fair Value Hedge Cumulative Increase Decrease HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease	29300000	USD
CY2019Q4	us-gaap	Fair Value Hedges At Fair Value Net FairValueHedgesAtFairValueNet	4729500000	USD
CY2019Q4	ntrs	Hedged Asset Liability Fair Value Hedge Cumulative Increase Decrease Net HedgedAssetLiabilityFairValueHedgeCumulativeIncreaseDecreaseNet	130200000	USD
CY2018Q4	us-gaap	Fair Value Hedges At Fair Value Net FairValueHedgesAtFairValueNet	5080400000	USD
CY2018Q4	ntrs	Hedged Asset Liability Fair Value Hedge Cumulative Increase Decrease Net HedgedAssetLiabilityFairValueHedgeCumulativeIncreaseDecreaseNet	128700000	USD
CY2019Q4	ntrs	Hedged Asset Fair Value Hedge Discontinued Cumulative Increase Decrease HedgedAssetFairValueHedgeDiscontinuedCumulativeIncreaseDecrease	1500000	USD
CY2019Q4	ntrs	Hedged Liability Fair Value Hedge Discontinued Cumulative Increase Decrease HedgedLiabilityFairValueHedgeDiscontinuedCumulativeIncreaseDecrease	0	USD
CY2018Q4	ntrs	Hedged Asset Liability Fair Value Hedge Discontinued Cumulative Increase Decrease Net HedgedAssetLiabilityFairValueHedgeDiscontinuedCumulativeIncreaseDecreaseNet	0	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	59700000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	173000000.0	USD
CY2019Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	2844000000.0	USD
CY2019Q4	us-gaap	Derivative Asset Fair Value Gross Liability DerivativeAssetFairValueGrossLiability	2338000000.0	USD
CY2019Q4	us-gaap	Derivative Fair Value Of Derivative Asset Amount Not Offset Against Collateral DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral	506000000.0	USD
CY2019Q4	us-gaap	Derivative Collateral Obligation To Return Cash DerivativeCollateralObligationToReturnCash	16500000	USD
CY2019Q4	us-gaap	Derivative Fair Value Of Derivative Asset Amount Offset Against Collateral DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral	489500000	USD
CY2019Q4	us-gaap	Derivative Asset Not Subject To Master Netting Arrangement DerivativeAssetNotSubjectToMasterNettingArrangement	543700000	USD
CY2019Q4	us-gaap	Derivative Asset Not Subject To Master Netting Arrangement DerivativeAssetNotSubjectToMasterNettingArrangement	543700000	USD
CY2019Q4	us-gaap	Derivative Asset Not Subject To Master Netting Arrangement Deduction DerivativeAssetNotSubjectToMasterNettingArrangementDeduction	300000	USD
CY2019Q4	ntrs	Derivative Asset Not Subjectto Master Netting Arrangement Net DerivativeAssetNotSubjecttoMasterNettingArrangementNet	543400000	USD
CY2019Q4	us-gaap	Derivative Asset Fair Value Gross Asset Including Not Subject To Master Netting Arrangement DerivativeAssetFairValueGrossAssetIncludingNotSubjectToMasterNettingArrangement	3387700000	USD
CY2019Q4	us-gaap	Derivative Asset Fair Value Gross Liability DerivativeAssetFairValueGrossLiability	2338000000.0	USD
CY2019Q4	us-gaap	Derivative Assets DerivativeAssets	1049700000	USD
CY2019Q4	ntrs	Derivative Asset Not Offset DerivativeAssetNotOffset	16800000	USD
CY2019Q4	us-gaap	Derivative Asset Fair Value Offset Against Collateral Net Of Not Subject To Master Netting Arrangement Policy Election DerivativeAssetFairValueOffsetAgainstCollateralNetOfNotSubjectToMasterNettingArrangementPolicyElection	1032900000	USD
CY2019Q4	us-gaap	Securities Purchased Under Agreements To Resell Gross SecuritiesPurchasedUnderAgreementsToResellGross	707800000	USD
CY2019Q4	us-gaap	Securities Purchased Under Agreements To Resell SecuritiesPurchasedUnderAgreementsToResell	707800000	USD
CY2019Q4	ntrs	Derivative Asset Securities Purchased Under Agreements To Resell Collateral DerivativeAssetSecuritiesPurchasedUnderAgreementsToResellCollateral	707800000	USD
CY2018Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	1999700000	USD
CY2018Q4	us-gaap	Derivative Asset Fair Value Gross Liability DerivativeAssetFairValueGrossLiability	1357100000	USD
CY2018Q4	us-gaap	Derivative Fair Value Of Derivative Asset Amount Not Offset Against Collateral DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral	642600000	USD
CY2018Q4	us-gaap	Derivative Collateral Obligation To Return Cash DerivativeCollateralObligationToReturnCash	12700000	USD
CY2018Q4	us-gaap	Derivative Fair Value Of Derivative Asset Amount Offset Against Collateral DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral	629900000	USD
CY2018Q4	us-gaap	Derivative Asset Not Subject To Master Netting Arrangement DerivativeAssetNotSubjectToMasterNettingArrangement	563800000	USD
CY2018Q4	us-gaap	Derivative Asset Not Subject To Master Netting Arrangement DerivativeAssetNotSubjectToMasterNettingArrangement	563800000	USD
CY2018Q4	us-gaap	Derivative Asset Not Subject To Master Netting Arrangement Deduction DerivativeAssetNotSubjectToMasterNettingArrangementDeduction	2700000	USD
CY2018Q4	ntrs	Derivative Asset Not Subjectto Master Netting Arrangement Net DerivativeAssetNotSubjecttoMasterNettingArrangementNet	561100000	USD
CY2018Q4	us-gaap	Derivative Asset Fair Value Gross Asset Including Not Subject To Master Netting Arrangement DerivativeAssetFairValueGrossAssetIncludingNotSubjectToMasterNettingArrangement	2563500000	USD
CY2018Q4	us-gaap	Derivative Asset Fair Value Gross Liability DerivativeAssetFairValueGrossLiability	1357100000	USD
CY2018Q4	us-gaap	Derivative Assets DerivativeAssets	1206400000	USD
CY2018Q4	ntrs	Derivative Asset Not Offset DerivativeAssetNotOffset	15400000	USD
CY2018Q4	us-gaap	Derivative Asset Fair Value Offset Against Collateral Net Of Not Subject To Master Netting Arrangement Policy Election DerivativeAssetFairValueOffsetAgainstCollateralNetOfNotSubjectToMasterNettingArrangementPolicyElection	1191000000.0	USD
CY2018Q4	us-gaap	Securities Purchased Under Agreements To Resell Gross SecuritiesPurchasedUnderAgreementsToResellGross	1031200000	USD
CY2018Q4	us-gaap	Securities Purchased Under Agreements To Resell SecuritiesPurchasedUnderAgreementsToResell	1031200000	USD
CY2018Q4	ntrs	Derivative Asset Securities Purchased Under Agreements To Resell Collateral DerivativeAssetSecuritiesPurchasedUnderAgreementsToResellCollateral	1031200000	USD
CY2019Q4	ntrs	Other Assets Excluding Derivatives And Non Financial Instruments OtherAssetsExcludingDerivativesAndNonFinancialInstruments	7400000000	USD
CY2018Q4	ntrs	Other Assets Excluding Derivatives And Non Financial Instruments OtherAssetsExcludingDerivativesAndNonFinancialInstruments	4600000000	USD
CY2019Q4	us-gaap	Federal Funds Sold FederalFundsSold	5000000.0	USD
CY2018Q4	us-gaap	Federal Funds Sold FederalFundsSold	134000000.0	USD
CY2019Q4	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	2312400000	USD
CY2019Q4	us-gaap	Derivative Liability Fair Value Gross Asset DerivativeLiabilityFairValueGrossAsset	1618400000	USD
CY2019Q4	us-gaap	Derivative Fair Value Of Derivative Liability Amount Not Offset Against Collateral DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral	694000000.0	USD
CY2019Q4	us-gaap	Derivative Collateral Right To Reclaim Cash DerivativeCollateralRightToReclaimCash	100000	USD
CY2019Q4	us-gaap	Derivative Fair Value Of Derivative Liability Amount Offset Against Collateral DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral	693900000	USD
CY2019Q4	us-gaap	Derivative Liability Not Subject To Master Netting Arrangement DerivativeLiabilityNotSubjectToMasterNettingArrangement	1000600000	USD
CY2019Q4	us-gaap	Derivative Liability Not Subject To Master Netting Arrangement DerivativeLiabilityNotSubjectToMasterNettingArrangement	1000600000	USD
CY2019Q4	us-gaap	Derivative Liability Not Subject To Master Netting Arrangement DerivativeLiabilityNotSubjectToMasterNettingArrangement	1000600000	USD
CY2019Q4	us-gaap	Derivative Liability Fair Value Gross Liability Including Not Subject To Master Netting Arrangement DerivativeLiabilityFairValueGrossLiabilityIncludingNotSubjectToMasterNettingArrangement	3313000000.0	USD
CY2019Q4	us-gaap	Derivative Liability Fair Value Gross Asset DerivativeLiabilityFairValueGrossAsset	1618400000	USD
CY2019Q4	us-gaap	Derivative Liabilities DerivativeLiabilities	1694600000	USD
CY2019Q4	us-gaap	Derivative Liability Not Subject To Master Netting Arrangement Deduction DerivativeLiabilityNotSubjectToMasterNettingArrangementDeduction	100000	USD
CY2019Q4	us-gaap	Derivative Liability Fair Value Offset Against Collateral Net Of Not Subject To Master Netting Arrangement Policy Election DerivativeLiabilityFairValueOffsetAgainstCollateralNetOfNotSubjectToMasterNettingArrangementPolicyElection	1694500000	USD
CY2019Q4	us-gaap	Securities Sold Under Agreements To Repurchase Gross SecuritiesSoldUnderAgreementsToRepurchaseGross	489700000	USD
CY2019Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	489700000	USD
CY2019Q4	ntrs	Derivative Liability Securities Sold Under Agreement To Repurchase Collateral DerivativeLiabilitySecuritiesSoldUnderAgreementToRepurchaseCollateral	489700000	USD
CY2018Q4	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	1947000000.0	USD
CY2018Q4	us-gaap	Derivative Liability Fair Value Gross Asset DerivativeLiabilityFairValueGrossAsset	1796300000	USD
CY2018Q4	us-gaap	Derivative Fair Value Of Derivative Liability Amount Not Offset Against Collateral DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral	150700000	USD
CY2018Q4	us-gaap	Derivative Fair Value Of Derivative Liability Amount Offset Against Collateral DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral	150700000	USD
CY2018Q4	us-gaap	Derivative Liability Not Subject To Master Netting Arrangement DerivativeLiabilityNotSubjectToMasterNettingArrangement	441400000	USD
CY2018Q4	us-gaap	Derivative Liability Not Subject To Master Netting Arrangement DerivativeLiabilityNotSubjectToMasterNettingArrangement	441400000	USD
CY2018Q4	us-gaap	Derivative Liability Not Subject To Master Netting Arrangement DerivativeLiabilityNotSubjectToMasterNettingArrangement	441400000	USD
CY2018Q4	us-gaap	Derivative Liability Fair Value Gross Liability Including Not Subject To Master Netting Arrangement DerivativeLiabilityFairValueGrossLiabilityIncludingNotSubjectToMasterNettingArrangement	2388400000	USD
CY2018Q4	us-gaap	Derivative Liability Fair Value Gross Asset DerivativeLiabilityFairValueGrossAsset	1796300000	USD
CY2018Q4	us-gaap	Derivative Liabilities DerivativeLiabilities	592100000	USD
CY2018Q4	us-gaap	Derivative Liability Fair Value Offset Against Collateral Net Of Not Subject To Master Netting Arrangement Policy Election DerivativeLiabilityFairValueOffsetAgainstCollateralNetOfNotSubjectToMasterNettingArrangementPolicyElection	592100000	USD
CY2018Q4	us-gaap	Securities Sold Under Agreements To Repurchase Gross SecuritiesSoldUnderAgreementsToRepurchaseGross	168300000	USD
CY2018Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	168300000	USD
CY2018Q4	ntrs	Derivative Liability Securities Sold Under Agreement To Repurchase Collateral DerivativeLiabilitySecuritiesSoldUnderAgreementToRepurchaseCollateral	168300000	USD
CY2019Q4	ntrs	Other Liabilities Excluding Derivatives And Non Financial Instruments OtherLiabilitiesExcludingDerivativesAndNonFinancialInstruments	3100000000	USD
CY2018Q4	ntrs	Other Liabilities Excluding Derivatives And Non Financial Instruments OtherLiabilitiesExcludingDerivativesAndNonFinancialInstruments	2500000000	USD
CY2019Q4	us-gaap	Derivative Net Liability Position Aggregate Fair Value DerivativeNetLiabilityPositionAggregateFairValue	766200000	USD
CY2018Q4	us-gaap	Derivative Net Liability Position Aggregate Fair Value DerivativeNetLiabilityPositionAggregateFairValue	324100000	USD
CY2019Q4	us-gaap	Collateral Already Posted Aggregate Fair Value CollateralAlreadyPostedAggregateFairValue	327100000	USD
CY2018Q4	us-gaap	Collateral Already Posted Aggregate Fair Value CollateralAlreadyPostedAggregateFairValue	316500000	USD
CY2019Q4	us-gaap	Assets Needed For Immediate Settlement Aggregate Fair Value AssetsNeededForImmediateSettlementAggregateFairValue	439100000	USD
CY2018Q4	us-gaap	Assets Needed For Immediate Settlement Aggregate Fair Value AssetsNeededForImmediateSettlementAggregateFairValue	7600000	USD
CY2019Q4	ntrs	Securities Lending Related Collateral Maintenance SecuritiesLendingRelatedCollateralMaintenance	1
CY2019Q4	us-gaap	Fair Value Investments Entities That Calculate Net Asset Value Per Share Unfunded Committments FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareUnfundedCommittments	0	USD
CY2018Q4	us-gaap	Fair Value Investments Entities That Calculate Net Asset Value Per Share Unfunded Committments FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareUnfundedCommittments	0	USD
CY2019Q4	us-gaap	Security Owned And Pledged As Collateral Fair Value SecurityOwnedAndPledgedAsCollateralFairValue	42100000000	USD
CY2018Q4	us-gaap	Security Owned And Pledged As Collateral Fair Value SecurityOwnedAndPledgedAsCollateralFairValue	39600000000	USD
CY2019Q4	us-gaap	Financial Instruments Owned And Pledged As Collateral Amount Eligible To Be Repledged By Counterparty FinancialInstrumentsOwnedAndPledgedAsCollateralAmountEligibleToBeRepledgedByCounterparty	487200000	USD
CY2018Q4	us-gaap	Financial Instruments Owned And Pledged As Collateral Amount Eligible To Be Repledged By Counterparty FinancialInstrumentsOwnedAndPledgedAsCollateralAmountEligibleToBeRepledgedByCounterparty	151500000	USD
CY2019Q4	us-gaap	Collateral Securities Repledged Delivered Or Used CollateralSecuritiesRepledgedDeliveredOrUsed	0	USD
CY2019Q4	us-gaap	Securities Held As Collateral At Fair Value SecuritiesHeldAsCollateralAtFairValue	707800000	USD
CY2018Q4	us-gaap	Securities Held As Collateral At Fair Value SecuritiesHeldAsCollateralAtFairValue	426200000	USD
CY2019	ntrs	Average Interest Bearing Deposits In Federal Reserve Bank For Reserve Requirements AverageInterestBearingDepositsInFederalReserveBankForReserveRequirements	1500000000	USD
CY2018	ntrs	Average Interest Bearing Deposits In Federal Reserve Bank For Reserve Requirements AverageInterestBearingDepositsInFederalReserveBankForReserveRequirements	1700000000	USD
CY2019	ntrs	Numberof Client Focused Reportable Segment NumberofClientFocusedReportableSegment	2	Segment
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3852100000	USD
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3753700000	USD
CY2017	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3434300000	USD
CY2019	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	250900000	USD
CY2018	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	307200000	USD
CY2017	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	209900000	USD
CY2019	us-gaap	Noninterest Income Other NoninterestIncomeOther	292200000	USD
CY2018	us-gaap	Noninterest Income Other NoninterestIncomeOther	276600000	USD
CY2017	us-gaap	Noninterest Income Other NoninterestIncomeOther	301900000	USD
CY2019	us-gaap	Noninterest Income NoninterestIncome	4395200000	USD
CY2018	us-gaap	Noninterest Income NoninterestIncome	4337500000	USD
CY2017	us-gaap	Noninterest Income NoninterestIncome	3946100000	USD
CY2019	ntrs	Interest Revenue Expense Net Including Fully Taxable Equivalent Adjustment InterestRevenueExpenseNetIncludingFullyTaxableEquivalentAdjustment	1710700000	USD
CY2018	ntrs	Interest Revenue Expense Net Including Fully Taxable Equivalent Adjustment InterestRevenueExpenseNetIncludingFullyTaxableEquivalentAdjustment	1663900000	USD
CY2017	ntrs	Interest Revenue Expense Net Including Fully Taxable Equivalent Adjustment InterestRevenueExpenseNetIncludingFullyTaxableEquivalentAdjustment	1475000000.0	USD
CY2019	ntrs	Revenue Including Fully Taxable Equivalent Adjustment RevenueIncludingFullyTaxableEquivalentAdjustment	6105900000	USD
CY2018	ntrs	Revenue Including Fully Taxable Equivalent Adjustment RevenueIncludingFullyTaxableEquivalentAdjustment	6001400000	USD
CY2017	ntrs	Revenue Including Fully Taxable Equivalent Adjustment RevenueIncludingFullyTaxableEquivalentAdjustment	5421100000	USD
CY2019	ntrs	Provision For Recovery Of Loan And Lease Losses ProvisionForRecoveryOfLoanAndLeaseLosses	-14500000	USD
CY2018	ntrs	Provision For Recovery Of Loan And Lease Losses ProvisionForRecoveryOfLoanAndLeaseLosses	-14500000	USD
CY2017	ntrs	Provision For Recovery Of Loan And Lease Losses ProvisionForRecoveryOfLoanAndLeaseLosses	-28000000.0	USD
CY2019	us-gaap	Noninterest Expense NoninterestExpense	4143500000	USD
CY2018	us-gaap	Noninterest Expense NoninterestExpense	4016900000	USD
CY2017	us-gaap	Noninterest Expense NoninterestExpense	3769400000	USD
CY2019	ntrs	Income Loss Before Income Taxes Including Fully Taxable Equivalent Adjustment IncomeLossBeforeIncomeTaxesIncludingFullyTaxableEquivalentAdjustment	1976900000	USD
CY2018	ntrs	Income Loss Before Income Taxes Including Fully Taxable Equivalent Adjustment IncomeLossBeforeIncomeTaxesIncludingFullyTaxableEquivalentAdjustment	1999000000.0	USD
CY2017	ntrs	Income Loss Before Income Taxes Including Fully Taxable Equivalent Adjustment IncomeLossBeforeIncomeTaxesIncludingFullyTaxableEquivalentAdjustment	1679700000	USD
CY2019	ntrs	Income Tax Expense Benefit Including Fully Taxable Equivalent Adjustment IncomeTaxExpenseBenefitIncludingFullyTaxableEquivalentAdjustment	484700000	USD
CY2018	ntrs	Income Tax Expense Benefit Including Fully Taxable Equivalent Adjustment IncomeTaxExpenseBenefitIncludingFullyTaxableEquivalentAdjustment	442600000	USD
CY2017	ntrs	Income Tax Expense Benefit Including Fully Taxable Equivalent Adjustment IncomeTaxExpenseBenefitIncludingFullyTaxableEquivalentAdjustment	480700000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	1492200000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	1556400000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	1199000000.0	USD
CY2019	ntrs	Segment Reporting Information Consolidated Average Assets SegmentReportingInformationConsolidatedAverageAssets	117551400000	USD
CY2018	ntrs	Segment Reporting Information Consolidated Average Assets SegmentReportingInformationConsolidatedAverageAssets	122946600000	USD
CY2017	ntrs	Segment Reporting Information Consolidated Average Assets SegmentReportingInformationConsolidatedAverageAssets	119607400000	USD
CY2019	ntrs	Segment Reporting Information Fully Taxable Equivalent Adjustment SegmentReportingInformationFullyTaxableEquivalentAdjustment	32800000	USD
CY2018	ntrs	Segment Reporting Information Fully Taxable Equivalent Adjustment SegmentReportingInformationFullyTaxableEquivalentAdjustment	41200000	USD
CY2017	ntrs	Segment Reporting Information Fully Taxable Equivalent Adjustment SegmentReportingInformationFullyTaxableEquivalentAdjustment	45800000	USD
CY2019Q4	us-gaap	Assets Assets	136828400000	USD
CY2019	us-gaap	Revenues Revenues	6073100000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	1944100000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	1492200000	USD
CY2018Q4	us-gaap	Assets Assets	132212500000	USD
CY2018	us-gaap	Revenues Revenues	5960200000	USD
CY2017Q4	us-gaap	Assets Assets	138590500000	USD
CY2017	us-gaap	Revenues Revenues	5375300000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	1957800000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	1556400000	USD
CY2017	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	1633900000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	1199000000.0	USD
CY2019Q4	ntrs	Supplementary Leverage Risk Based Capital Requiredtobe Well Capitalizedto Risk Weighted Assets SupplementaryLeverageRiskBasedCapitalRequiredtobeWellCapitalizedtoRiskWeightedAssets	0.03

Files In Submission

Name	View Source	Status
0000073124-20-000101-index-headers.html	Edgar Link	pending
0000073124-20-000101-index.html	Edgar Link	pending
0000073124-20-000101.txt	Edgar Link	pending
0000073124-20-000101-xbrl.zip	Edgar Link	pending
a201910-k.htm	Edgar Link	pending
a201910-kex1018i.htm	Edgar Link	pending
a201910-kex44.htm	Edgar Link	pending
a201910-kexx1018ii.htm	Edgar Link	pending
a201910-kexx1019.htm	Edgar Link	pending
a201910-kexx1020.htm	Edgar Link	pending
a201910-kexx21.htm	Edgar Link	pending
a201910-kexx23.htm	Edgar Link	pending
a201910-kexx311.htm	Edgar Link	pending
a201910-kexx312.htm	Edgar Link	pending
a201910-kexx32.htm	Edgar Link	pending
a201910-k_htm.xml	Edgar Link	completed
chart-2d8fe66c83e950e09cd.jpg	Edgar Link	pending
chart-3c823ef063365e3cbea.jpg	Edgar Link	pending
chart-464fb0822ba256c6a4d.jpg	Edgar Link	pending
chart-509823f5b6005b5ea05.jpg	Edgar Link	pending
chart-69ece86afc0a56e5b12.jpg	Edgar Link	pending
chart-999274a84dd359beb1c.jpg	Edgar Link	pending
chart-a18dc5bf54a95478b70.jpg	Edgar Link	pending
chart-b9aa39afdafe50f9bd1.jpg	Edgar Link	pending
chart-bdefc99495b75ebb8c2.jpg	Edgar Link	pending
chart-e339603e71175933909.jpg	Edgar Link	pending
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
kpmghighresa19.jpg	Edgar Link	pending
MetaLinks.json	Edgar Link	pending
ntrs-20191231.xsd	Edgar Link	pending
ntrs-20191231_cal.xml	Edgar Link	unprocessable
ntrs-20191231_def.xml	Edgar Link	unprocessable
ntrs-20191231_lab.xml	Edgar Link	unprocessable
ntrs-20191231_pre.xml	Edgar Link	unprocessable
R1.htm	Edgar Link	pending
R10.htm	Edgar Link	pending
R100.htm	Edgar Link	pending
R101.htm	Edgar Link	pending
R102.htm	Edgar Link	pending
R103.htm	Edgar Link	pending
R104.htm	Edgar Link	pending
R105.htm	Edgar Link	pending
R106.htm	Edgar Link	pending
R107.htm	Edgar Link	pending
R108.htm	Edgar Link	pending
R109.htm	Edgar Link	pending
R11.htm	Edgar Link	pending
R110.htm	Edgar Link	pending
R111.htm	Edgar Link	pending
R112.htm	Edgar Link	pending
R113.htm	Edgar Link	pending
R114.htm	Edgar Link	pending
R115.htm	Edgar Link	pending
R116.htm	Edgar Link	pending
R117.htm	Edgar Link	pending
R118.htm	Edgar Link	pending
R119.htm	Edgar Link	pending
R12.htm	Edgar Link	pending
R120.htm	Edgar Link	pending
R121.htm	Edgar Link	pending
R122.htm	Edgar Link	pending
R123.htm	Edgar Link	pending
R124.htm	Edgar Link	pending
R125.htm	Edgar Link	pending
R126.htm	Edgar Link	pending
R127.htm	Edgar Link	pending
R128.htm	Edgar Link	pending
R129.htm	Edgar Link	pending
R13.htm	Edgar Link	pending
R130.htm	Edgar Link	pending
R131.htm	Edgar Link	pending
R132.htm	Edgar Link	pending
R133.htm	Edgar Link	pending
R134.htm	Edgar Link	pending
R135.htm	Edgar Link	pending
R136.htm	Edgar Link	pending
R137.htm	Edgar Link	pending
R138.htm	Edgar Link	pending
R139.htm	Edgar Link	pending
R14.htm	Edgar Link	pending
R140.htm	Edgar Link	pending
R141.htm	Edgar Link	pending
R142.htm	Edgar Link	pending
R143.htm	Edgar Link	pending
R144.htm	Edgar Link	pending
R145.htm	Edgar Link	pending
R146.htm	Edgar Link	pending
R147.htm	Edgar Link	pending
R148.htm	Edgar Link	pending
R149.htm	Edgar Link	pending
R15.htm	Edgar Link	pending
R150.htm	Edgar Link	pending
R151.htm	Edgar Link	pending
R152.htm	Edgar Link	pending
R153.htm	Edgar Link	pending
R154.htm	Edgar Link	pending
R155.htm	Edgar Link	pending
R156.htm	Edgar Link	pending
R157.htm	Edgar Link	pending
R158.htm	Edgar Link	pending
R159.htm	Edgar Link	pending
R16.htm	Edgar Link	pending
R160.htm	Edgar Link	pending
R161.htm	Edgar Link	pending
R162.htm	Edgar Link	pending
R163.htm	Edgar Link	pending
R164.htm	Edgar Link	pending
R165.htm	Edgar Link	pending
R166.htm	Edgar Link	pending
R167.htm	Edgar Link	pending
R168.htm	Edgar Link	pending
R169.htm	Edgar Link	pending
R17.htm	Edgar Link	pending
R170.htm	Edgar Link	pending
R171.htm	Edgar Link	pending
R172.htm	Edgar Link	pending
R173.htm	Edgar Link	pending
R174.htm	Edgar Link	pending
R175.htm	Edgar Link	pending
R176.htm	Edgar Link	pending
R177.htm	Edgar Link	pending
R178.htm	Edgar Link	pending
R179.htm	Edgar Link	pending
R18.htm	Edgar Link	pending
R180.htm	Edgar Link	pending
R181.htm	Edgar Link	pending
R182.htm	Edgar Link	pending
R183.htm	Edgar Link	pending
R184.htm	Edgar Link	pending
R185.htm	Edgar Link	pending
R186.htm	Edgar Link	pending
R187.htm	Edgar Link	pending
R19.htm	Edgar Link	pending
R2.htm	Edgar Link	pending
R20.htm	Edgar Link	pending
R21.htm	Edgar Link	pending
R22.htm	Edgar Link	pending
R23.htm	Edgar Link	pending
R24.htm	Edgar Link	pending
R25.htm	Edgar Link	pending
R26.htm	Edgar Link	pending
R27.htm	Edgar Link	pending
R28.htm	Edgar Link	pending
R29.htm	Edgar Link	pending
R3.htm	Edgar Link	pending
R30.htm	Edgar Link	pending
R31.htm	Edgar Link	pending
R32.htm	Edgar Link	pending
R33.htm	Edgar Link	pending
R34.htm	Edgar Link	pending
R35.htm	Edgar Link	pending
R36.htm	Edgar Link	pending
R37.htm	Edgar Link	pending
R38.htm	Edgar Link	pending
R39.htm	Edgar Link	pending
R4.htm	Edgar Link	pending
R40.htm	Edgar Link	pending
R41.htm	Edgar Link	pending
R42.htm	Edgar Link	pending
R43.htm	Edgar Link	pending
R44.htm	Edgar Link	pending
R45.htm	Edgar Link	pending
R46.htm	Edgar Link	pending
R47.htm	Edgar Link	pending
R48.htm	Edgar Link	pending
R49.htm	Edgar Link	pending
R5.htm	Edgar Link	pending
R50.htm	Edgar Link	pending
R51.htm	Edgar Link	pending
R52.htm	Edgar Link	pending
R53.htm	Edgar Link	pending
R54.htm	Edgar Link	pending
R55.htm	Edgar Link	pending
R56.htm	Edgar Link	pending
R57.htm	Edgar Link	pending
R58.htm	Edgar Link	pending
R59.htm	Edgar Link	pending
R6.htm	Edgar Link	pending
R60.htm	Edgar Link	pending
R61.htm	Edgar Link	pending
R62.htm	Edgar Link	pending
R63.htm	Edgar Link	pending
R64.htm	Edgar Link	pending
R65.htm	Edgar Link	pending
R66.htm	Edgar Link	pending
R67.htm	Edgar Link	pending
R68.htm	Edgar Link	pending
R69.htm	Edgar Link	pending
R7.htm	Edgar Link	pending
R70.htm	Edgar Link	pending
R71.htm	Edgar Link	pending
R72.htm	Edgar Link	pending
R73.htm	Edgar Link	pending
R74.htm	Edgar Link	pending
R75.htm	Edgar Link	pending
R76.htm	Edgar Link	pending
R77.htm	Edgar Link	pending
R78.htm	Edgar Link	pending
R79.htm	Edgar Link	pending
R8.htm	Edgar Link	pending
R80.htm	Edgar Link	pending
R81.htm	Edgar Link	pending
R82.htm	Edgar Link	pending
R83.htm	Edgar Link	pending
R84.htm	Edgar Link	pending
R85.htm	Edgar Link	pending
R86.htm	Edgar Link	pending
R87.htm	Edgar Link	pending
R88.htm	Edgar Link	pending
R89.htm	Edgar Link	pending
R9.htm	Edgar Link	pending
R90.htm	Edgar Link	pending
R91.htm	Edgar Link	pending
R92.htm	Edgar Link	pending
R93.htm	Edgar Link	pending
R94.htm	Edgar Link	pending
R95.htm	Edgar Link	pending
R96.htm	Edgar Link	pending
R97.htm	Edgar Link	pending
R98.htm	Edgar Link	pending
R99.htm	Edgar Link	pending
R9999.htm	Edgar Link	pending
report.css	Edgar Link	pending
Show.js	Edgar Link	pending

Create your account

Find Stocks Worth Researching

Deeply Understand Businesses

Value Businesses Intelligently

$NTRS
NORTHERN TRUST CORP Stock $ntrs

2018 Q4 Form 10-K Financial Statement

#000007312420000101 Filed on February 25, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$NTRS NORTHERN TRUST CORP Stock $ntrs

2018 Q4 Form 10-K Financial Statement

#000007312420000101 Filed on February 25, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$NTRS
NORTHERN TRUST CORP Stock $ntrs