$NTRS
NORTHERN TRUST CORP Stock $ntrs

$ntrs Overview Financials Valuation SEC Filings Company Website

2019 Q4 Form 10-K Financial Statement

#000007312421000071 Filed on February 23, 2021

Income Statement

Concept	2019 Q4	2018 Q4	2018
Revenue	$1.639B	$1.662B	$5.960B
YoY Change	-1.37%	11.46%	10.88%
Cost Of Revenue	$91.30M	$157.9M	$450.2M
YoY Change	-42.18%	137.8%	121.34%
Gross Profit	$1.548B	$1.504B	$5.960B
YoY Change	2.92%	5.57%	10.88%
Gross Profit Margin	94.43%	90.5%	100.0%
Selling, General & Admin	$818.5M	$767.1M	$3.069B
YoY Change	6.7%	1.87%	7.15%
% of Gross Profit	52.88%	51.01%	51.49%
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$117.3M	$114.0M	$460.9M
YoY Change	2.89%	3.17%	9.3%
% of Gross Profit	7.58%	7.58%	7.73%
Operating Expenses	$1.071B	$1.018B	$3.984B
YoY Change	5.25%	4.54%	7.75%
Operating Profit	$476.4M	$485.9M	$1.976B
YoY Change	-1.96%	7.79%	17.77%
Interest Expense			$698.7M
YoY Change			105.38%
% of Operating Profit			35.36%
Other Income/Expense, Net
YoY Change
Pretax Income	$476.4M	$485.9M	$1.958B
YoY Change	-1.96%	11.55%	19.82%
Income Tax	$105.3M	$91.10M	$401.4M
% Of Pretax Income	22.1%	18.75%	20.5%
Net Earnings	$371.1M	$409.9M	$1.556B
YoY Change	-9.47%	14.95%	29.81%
Net Earnings / Revenue	22.64%	24.67%	26.11%
Basic Earnings Per Share			$6.68
Diluted Earnings Per Share	$1.752M	$1.851M	$6.64
COMMON SHARES
Basic Shares Outstanding			223.1M shares
Diluted Shares Outstanding			224.5M shares

Balance Sheet

Concept	2019 Q4	2018 Q4	2018
SHORT-TERM ASSETS
Cash & Short-Term Investments	$55.62B	$55.82B	$4.582B
YoY Change	-0.37%	8.8%	1.42%
Cash & Equivalents	$4.459B	$4.582B
Short-Term Investments	$51.16B	$51.24B
Other Short-Term Assets
YoY Change
Inventory
Prepaid Expenses
Receivables
Other Receivables
Total Short-Term Assets	$4.459B	$4.582B	$4.582B
YoY Change	-2.68%	1.42%	1.42%
LONG-TERM ASSETS
Property, Plant & Equipment	$483.3M	$428.2M	$428.0M
YoY Change	12.87%	-7.83%	-7.96%
Goodwill	$696.8M	$669.3M
YoY Change	4.11%	10.52%
Intangibles
YoY Change
Long-Term Investments	$90.64B	$86.75B	$86.75B
YoY Change	4.48%	-7.91%	-7.91%
Other Assets
YoY Change
Total Long-Term Assets	$132.4B	$127.6B	$127.6B
YoY Change	3.71%	-4.8%	-4.8%
TOTAL ASSETS
Total Short-Term Assets	$4.459B	$4.582B	$4.582B
Total Long-Term Assets	$132.4B	$127.6B	$127.6B
Total Assets	$136.8B	$132.2B	$132.2B
YoY Change	3.49%	-4.6%	-4.6%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses	$603.0M
YoY Change
Deferred Revenue
YoY Change
Short-Term Debt	$110.2B	$107.3B	$107.3B
YoY Change	2.71%	-7.14%	-7.14%
Long-Term Debt Due	$6.745B	$7.902B	$7.902B
YoY Change	-14.64%	30.59%	30.59%
Total Short-Term Liabilities	$117.5B	$115.2B	$115.2B
YoY Change	2.04%	-5.27%	-5.27%
LONG-TERM LIABILITIES
Long-Term Debt	$3.999B	$3.401B	$3.401B
YoY Change	17.58%	5.49%	5.49%
Other Long-Term Liabilities	$4.228B	$3.142B	$3.142B
YoY Change	34.56%	-12.43%	-12.43%
Total Long-Term Liabilities	$8.227B	$6.543B	$6.543B
YoY Change	25.74%	-3.95%	-3.95%
TOTAL LIABILITIES
Total Short-Term Liabilities	$117.5B	$115.2B	$115.2B
Total Long-Term Liabilities	$8.227B	$6.543B	$6.543B
Total Liabilities	$125.7B	$121.7B	$121.7B
YoY Change	3.31%	-5.2%	-5.2%
SHAREHOLDERS EQUITY
Retained Earnings	$11.66B	$10.78B
YoY Change	8.16%	11.27%
Common Stock	$408.6M	$408.6M
YoY Change	0.0%	0.0%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$3.066B	$2.174B
YoY Change	41.04%	56.13%
Treasury Stock Shares	35.46M shares	26.16M shares
Shareholders Equity	$11.09B	$10.51B	$10.51B
YoY Change
Total Liabilities & Shareholders Equity	$136.8B	$132.2B	$132.2B
YoY Change	3.49%	-4.6%	-4.6%

Cashflow Statement

Concept	2019 Q4	2018 Q4	2018
OPERATING ACTIVITIES
Net Income	$371.1M	$409.9M	$1.556B
YoY Change	-9.47%	14.95%	29.81%
Depreciation, Depletion And Amortization	$117.3M	$114.0M	$460.9M
YoY Change	2.89%	3.17%	9.3%
Cash From Operating Activities	$482.4M	$459.1M	$1.768B
YoY Change	5.08%	-46.03%	2.74%
INVESTING ACTIVITIES
Capital Expenditures	-$245.3M	-$177.9M	$97.60M
YoY Change	37.89%	47.15%	6.55%
Acquisitions
YoY Change
Other Investing Activities	-$12.16B	-$843.2M	$873.6M
YoY Change	1341.9%	-89.37%	-3486.05%
Cash From Investing Activities	-$12.40B	-$1.021B	$4.327B
YoY Change	1114.71%	-87.32%	-130.86%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net			$924.3M
YoY Change			76.7%
Debt Paid & Issued, Net			$314.3M
YoY Change			50.6%
Cash From Financing Activities	10.11B	77.80M	-$5.818B
YoY Change	12901.03%	-98.79%	-151.7%
NET CHANGE
Cash From Operating Activities	482.4M	459.1M	$1.768B
Cash From Investing Activities	-12.40B	-1.021B	$4.327B
Cash From Financing Activities	10.11B	77.80M	-$5.818B
Net Change In Cash	-1.806B	-484.2M	$63.50M
YoY Change	273.03%	-37.04%	-107.8%
FREE CASH FLOW
Cash From Operating Activities	$482.4M	$459.1M	$1.768B
Capital Expenditures	-$245.3M	-$177.9M	$97.60M
Free Cash Flow	$727.7M	$637.0M	$1.670B
YoY Change	14.24%	-34.44%	2.52%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
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CY2020	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2020
CY2020	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
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CY2020	dei	Document Type DocumentType	10-K
CY2020	dei	Document Annual Report DocumentAnnualReport	true
CY2020	dei	Document Period End Date DocumentPeriodEndDate	2020-12-31
CY2020	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2020	dei	Document Transition Report DocumentTransitionReport	false
CY2020	dei	Entity File Number EntityFileNumber	001-36609
CY2020	dei	Entity Registrant Name EntityRegistrantName	NORTHERN TRUST CORPORATION
CY2020	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	DE
CY2020	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	36-2723087
CY2020	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2020	dei	Entity Address Address Line1 EntityAddressAddressLine1	50 South La Salle Street
CY2020	dei	Entity Address City Or Town EntityAddressCityOrTown	Chicago,
CY2020	dei	Entity Address State Or Province EntityAddressStateOrProvince	IL
CY2020	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	60603
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CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	451900000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	401400000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	1209300000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	1492200000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	1556400000	USD
CY2020	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	56200000	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
CY2020	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	1153100000	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
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	5.48
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	6.66
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	6.68
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	5.46
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	6.63
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	6.64
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	208319412	shares
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
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	209007986	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
CY2020	ntrs	Other Than Temporary Impairment Losses OtherThanTemporaryImpairmentLosses	0	USD
CY2019	ntrs	Other Than Temporary Impairment Losses OtherThanTemporaryImpairmentLosses	300000	USD
CY2018	ntrs	Other Than Temporary Impairment Losses OtherThanTemporaryImpairmentLosses	500000	USD
CY2020	ntrs	Investment Security Gains Losses Net InvestmentSecurityGainsLossesNet	-400000	USD
CY2019	ntrs	Investment Security Gains Losses Net InvestmentSecurityGainsLossesNet	-1100000	USD
CY2018	ntrs	Investment Security Gains Losses Net InvestmentSecurityGainsLossesNet	-500000	USD
CY2020	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-400000	USD
CY2019	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1400000	USD
CY2018	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1000000.0	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	1209300000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	1492200000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	1556400000	USD
CY2020	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	527800000	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
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax Parent OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent	500000	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
CY2020	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	26900000	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
CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-67500000	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
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	622700000	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
CY2020	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	1832000000.0	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	1751200000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	1542300000	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
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	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.94
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	164100000	USD
CY2018	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	924300000	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	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	2.60
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	152600000	USD
CY2019	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	1100200000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	11091000000.0	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	1209300000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	622700000	USD
CY2020	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	2.80
CY2020	us-gaap	Dividends Common Stock DividendsCommonStock	592000000.0	USD
CY2020	us-gaap	Dividends Preferred Stock DividendsPreferredStock	44700000	USD
CY2020	us-gaap	Stock Redeemed Or Called During Period Value StockRedeemedOrCalledDuringPeriodValue	400000000.0	USD
CY2020	us-gaap	Stock Issued During Period Value Share Based Compensation StockIssuedDuringPeriodValueShareBasedCompensation	111900000	USD
CY2020	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	299800000	USD
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	11688300000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	1209300000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	1492200000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	1556400000	USD
CY2020	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-400000	USD
CY2019	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1400000	USD
CY2018	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1000000.0	USD
CY2020	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-88900000	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
CY2020	ntrs	Credit Loss Expense Reversal And Available For Sale Allowance For Credit Loss CreditLossExpenseReversalAndAvailableForSaleAllowanceForCreditLoss	125000000.0	USD
CY2019	ntrs	Credit Loss Expense Reversal And Available For Sale Allowance For Credit Loss CreditLossExpenseReversalAndAvailableForSaleAllowanceForCreditLoss	-14500000	USD
CY2018	ntrs	Credit Loss Expense Reversal And Available For Sale Allowance For Credit Loss CreditLossExpenseReversalAndAvailableForSaleAllowanceForCreditLoss	-14500000	USD
CY2020	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	500300000	USD
CY2019	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	458900000	USD
CY2018	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	460900000	USD
CY2020	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	25400000	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
CY2020	us-gaap	Pension Contributions PensionContributions	15600000	USD
CY2019	us-gaap	Pension Contributions PensionContributions	6100000	USD
CY2018	us-gaap	Pension Contributions PensionContributions	74500000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	16400000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	34300000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	10500000	USD
CY2020	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	-4500000	USD
CY2019	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	50300000	USD
CY2018	us-gaap	Increase Decrease In Receivables IncreaseDecreaseInReceivables	197000000.0	USD
CY2020	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	-23600000	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
CY2020	us-gaap	Increase Decrease In Derivative Assets IncreaseDecreaseInDerivativeAssets	17800000	USD
CY2019	us-gaap	Increase Decrease In Derivative Assets IncreaseDecreaseInDerivativeAssets	-1154000000.0	USD
CY2018	us-gaap	Increase Decrease In Derivative Assets IncreaseDecreaseInDerivativeAssets	699600000	USD
CY2020	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	16400000	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
CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	1896800000	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
CY2020	ntrs	Proceeds From Payments For Federal Funds Sold ProceedsFromPaymentsForFederalFundsSold	5000000.0	USD
CY2019	ntrs	Proceeds From Payments For Federal Funds Sold ProceedsFromPaymentsForFederalFundsSold	129000000.0	USD
CY2018	ntrs	Proceeds From Payments For Federal Funds Sold ProceedsFromPaymentsForFederalFundsSold	-113000000.0	USD
CY2020	us-gaap	Proceeds From Payments For Securities Purchased Under Agreements To Resell ProceedsFromPaymentsForSecuritiesPurchasedUnderAgreementsToResell	-700900000	USD
CY2019	us-gaap	Proceeds From Payments For Securities Purchased Under Agreements To Resell ProceedsFromPaymentsForSecuritiesPurchasedUnderAgreementsToResell	357300000	USD
CY2018	us-gaap	Proceeds From Payments For Securities Purchased Under Agreements To Resell ProceedsFromPaymentsForSecuritiesPurchasedUnderAgreementsToResell	218700000	USD
CY2020	us-gaap	Proceeds From Payments For In Interest Bearing Deposits In Banks ProceedsFromPaymentsForInInterestBearingDepositsInBanks	712600000	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
CY2020	ntrs	Payments For Proceeds From Federal Reserve And Foreign Central Bank Deposits PaymentsForProceedsFromFederalReserveAndForeignCentralBankDeposits	19845200000	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
CY2020	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	40187900000	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
CY2020	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	35658600000	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
CY2020	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	10886800000	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
CY2020	us-gaap	Proceeds From Sale And Maturity Of Available For Sale Securities ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities	8748200000	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
CY2020	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	2316700000	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
CY2020	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	135800000	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
CY2020	us-gaap	Payments For Software PaymentsForSoftware	424600000	USD
CY2019	us-gaap	Payments For Software PaymentsForSoftware	441800000	USD
CY2018	us-gaap	Payments For Software PaymentsForSoftware	408400000	USD
CY2020	ntrs	Net Change In Client Security Settlement Receivables NetChangeInClientSecuritySettlementReceivables	226800000	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
CY2020	us-gaap	Payments To Acquire Interest In Subsidiaries And Affiliates PaymentsToAcquireInterestInSubsidiariesAndAffiliates	0	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
CY2020	us-gaap	Payments To Acquire Life Insurance Policies PaymentsToAcquireLifeInsurancePolicies	0	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
CY2020	us-gaap	Payments For Proceeds From Other Investing Activities PaymentsForProceedsFromOtherInvestingActivities	322700000	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
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-29923000000.0	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
CY2020	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	32137900000	USD
CY2019	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	4263600000	USD
CY2018	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	-6163200000	USD
CY2020	ntrs	Change In Federal Funds Purchased ChangeInFederalFundsPurchased	292700000	USD
CY2019	ntrs	Change In Federal Funds Purchased ChangeInFederalFundsPurchased	2041300000	USD
CY2018	ntrs	Change In Federal Funds Purchased ChangeInFederalFundsPurchased	-308100000	USD
CY2020	us-gaap	Proceeds From Payments For In Securities Sold Under Agreements To Repurchase ProceedsFromPaymentsForInSecuritiesSoldUnderAgreementsToRepurchase	-450000000.0	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
CY2020	us-gaap	Proceeds From Repayments Of Short Term Debt Maturing In Three Months Or Less ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	-2698300000	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
CY2020	us-gaap	Payments For Repurchase Of Preferred Stock And Preference Stock PaymentsForRepurchaseOfPreferredStockAndPreferenceStock	400000000.0	USD
CY2019	us-gaap	Payments For Repurchase Of Preferred Stock And Preference Stock PaymentsForRepurchaseOfPreferredStockAndPreferenceStock	0	USD
CY2018	us-gaap	Payments For Repurchase Of Preferred Stock And Preference Stock PaymentsForRepurchaseOfPreferredStockAndPreferenceStock	0	USD
CY2020	us-gaap	Proceeds From Issuance Of Senior Long Term Debt ProceedsFromIssuanceOfSeniorLongTermDebt	993200000	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
CY2020	us-gaap	Repayments Of Senior Debt RepaymentsOfSeniorDebt	508600000	USD
CY2019	us-gaap	Repayments Of Senior Debt RepaymentsOfSeniorDebt	0	USD
CY2018	us-gaap	Repayments Of Senior Debt RepaymentsOfSeniorDebt	314300000	USD
CY2020	us-gaap	Proceeds From Issuance Of Preferred Stock And Preference Stock ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	0	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
CY2020	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	299800000	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
CY2020	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	19500000	USD
CY2019	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	44000000.0	USD
CY2018	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	32600000	USD
CY2020	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	584600000	USD
CY2019	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	529700000	USD
CY2018	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	405400000	USD
CY2020	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	45900000	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
CY2020	us-gaap	Proceeds From Payments For Other Financing Activities ProceedsFromPaymentsForOtherFinancingActivities	1200000	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
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	27871900000	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
CY2020	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	84600000	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
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-69700000	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
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
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	4389500000	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
CY2020	us-gaap	Interest Paid Net InterestPaidNet	226800000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	845500000	USD
CY2018	us-gaap	Interest Paid Net InterestPaidNet	670200000	USD
CY2020	us-gaap	Income Taxes Paid IncomeTaxesPaid	327700000	USD
CY2019	us-gaap	Income Taxes Paid IncomeTaxesPaid	437000000.0	USD
CY2018	us-gaap	Income Taxes Paid IncomeTaxesPaid	493500000	USD
CY2020	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	200000	USD
CY2019	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	3500000	USD
CY2018	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	11400000	USD
CY2020	us-gaap	Debt Securities Held To Maturity Transfer Amount DebtSecuritiesHeldToMaturityTransferAmount	301500000	USD
CY2019	us-gaap	Debt Securities Held To Maturity Transfer Amount DebtSecuritiesHeldToMaturityTransferAmount	160800000	USD
CY2018	us-gaap	Debt Securities Held To Maturity Transfer Amount DebtSecuritiesHeldToMaturityTransferAmount	0	USD
CY2020	us-gaap	Financing Receivable Reclassification To Held For Sale FinancingReceivableReclassificationToHeldForSale	0	USD
CY2019	us-gaap	Financing Receivable Reclassification To Held For Sale FinancingReceivableReclassificationToHeldForSale	53600000	USD
CY2018	us-gaap	Financing Receivable Reclassification To Held For Sale FinancingReceivableReclassificationToHeldForSale	0	USD
CY2020	ntrs	Numberof Client Focused Reportable Segment NumberofClientFocusedReportableSegment	2	segment
CY2020	us-gaap	Use Of Estimates UseOfEstimates	Use of Estimates in the Preparation of Financial Statements. 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.
CY2020	us-gaap	Description Of New Accounting Pronouncements Not Yet Adopted DescriptionOfNewAccountingPronouncementsNotYetAdopted	Recent Accounting Pronouncements<div style="margin-bottom:6pt;margin-top:6pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">On January 1, 2020, Northern Trust adopted Accounting Standards Update (ASU) No. 2016-13, “Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments” (ASU 2016-13). ASU 2016-13 significantly changed the way impairment of financial instruments is recognized by requiring immediate recognition of estimated credit losses expected to occur over the remaining life of financial instruments. The main provisions of ASU 2016-13 include (1) replacing the “incurred loss” approach under current GAAP with an “expected loss” model for instruments measured at amortized cost, (2) requiring entities to record an allowance for available for sale debt securities rather than reduce the carrying amount of the investments, as is required by the other-than-temporary-impairment model under legacy GAAP, and (3) a simplified accounting model for purchased credit-impaired debt securities and loans. </span></div><div style="margin-bottom:6pt;margin-top:6pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Upon adoption of ASU 2016-13, Northern Trust recorded a $13.7 million increase in the allowance for credit losses with a corresponding cumulative effect adjustment to decrease retained earnings by $10.1 million, net of income taxes, on January 1, 2020. Northern Trust did not restate comparative periods for the effects of applying ASU 2016-13. There was no significant impact to Northern Trust’s consolidated statements of income. Please refer to Note 7 — Allowance for Credit Losses for further information. </span></div><div style="margin-bottom:6pt;margin-top:6pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">On January 1, 2020, Northern Trust adopted ASU No. 2017-04, “Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment” (ASU 2017-04). ASU 2017-04 amends the subsequent measurement of goodwill whereby Step 2 from the goodwill impairment test is eliminated. As a result, the goodwill impairment test is performed by comparing the fair value of a reporting unit to its carrying value and an impairment charge should be recognized for the amount by which the carrying amount exceeds the reporting unit’s fair value, not to exceed the total amount of goodwill allocated to that reporting unit. Upon adoption of ASU 2017-04, there was no significant impact to Northern Trust’s consolidated balance sheets or consolidated statements of income. </span></div><div style="margin-bottom:6pt;margin-top:6pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">On January 1, 2020, Northern Trust adopted ASU No. 2018-13, “Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement” (ASU 2018-13). The primary objective of ASU 2018-13 is to improve the effectiveness of disclosures in the notes to financial statements. Upon adoption of ASU 2018-13, there was no significant impact to Northern Trust’s consolidated balance sheets or consolidated statements of income. </span></div><div style="margin-bottom:6pt;margin-top:6pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">On January 1, 2020, Northern Trust adopted ASU No. 2018-15, “Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (a consensus of the FASB Emerging Issues Task Force)” (ASU 2018-15). ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal use software license). Upon adoption of ASU 2018-15, there was no significant impact to Northern Trust’s consolidated balance sheets or consolidated statements of income. </span></div><div style="margin-bottom:6pt;margin-top:6pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">On January 1, 2020, Northern Trust adopted ASU No. 2018-17, “Consolidation (Topic 810): Targeted Improvements to Related Party Guidance for Variable Interest Entities” (ASU 2018-17). ASU 2018-17 requires that indirect interests held through related parties in common control arrangements be considered on a proportional basis (rather than as the equivalent of a direct interest in its entirety) for determining whether fees paid to decision makers and service providers are variable interests. Upon adoption of ASU 2018-17, there was no significant impact to Northern Trust’s consolidated balance sheets or consolidated statements of income. </span></div><div style="margin-bottom:6pt;margin-top:6pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">On April 1, 2020, Northern Trust adopted ASU No. 2020-04, “Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting” (ASU 2020-04). The global transition toward alternative reference rates and away from referencing the London Interbank Offered Rate (LIBOR) and other interbank offered rates (Reference Rate Reform) is expected to have a significant impact on the volume of contract modifications, hedge accounting, and other transactions that reference LIBOR or another reference rate expected to be discontinued because of Reference Rate Reform. ASU 2020-04 provides temporary optional expedients and exceptions for applying GAAP to contract modifications, hedging relationships, and other transactions affected by Reference Rate Reform if certain criteria are met. The main provisions of ASU 2020-04 provide the following optional expedients: (1) simplification of the accounting evaluations under current GAAP for contract modifications, including loan, debt, lease and other contracts with potential embedded derivatives, if qualifying criteria are met (2) preservation of hedging relationships without dedesignation upon certain changes to the critical terms of an existing hedging relationship due to Reference Rate Reform and other optional hedge accounting relief provisions and (3) a one-time election to sell or transfer, or both sell and </span></div><div style="margin-bottom:6pt;margin-top:6pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">transfer, debt securities classified as held to maturity that reference a rate affected by Reference Rate Reform and are classified as held to maturity before January 1, 2020. </span></div><div style="margin-bottom:6pt;margin-top:6pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The optional expedients in ASU 2020-04 for contract modifications and hedging relationships are applied prospectively, while the one-time election to sell or transfer, or both sell and transfer debt securities classified as held to maturity may be made at any time after March 12, 2020. The optional expedients and exceptions provided by ASU 2020-04 do not apply to contract modifications made and hedging relationships entered into or evaluated after December 31, 2022, except for hedging relationships existing as of December 31, 2022 for which an entity has elected certain optional expedients and which are retained through the end of the hedging relationship.</span><span style="color:#ff0000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Upon adoption of ASU 2020-04, there was no significant impact on Northern Trust’s consolidated balance sheets or consolidated statements of income. Northern Trust expects to elect the optional expedients provided in ASU 2020-04 and does not expect a significant impact on Northern Trust’s consolidated balance sheets or consolidated statements of income as a result of electing such expedients. </span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">On January 7, 2021, Northern Trust retrospectively adopted ASU No. 2021-01, “Reference Rate Reform (Topic 848): Scope” (ASU 2021-01). ASU 2021-01 clarifies the scope of Topic 848 to explicitly include those derivative instruments affected by changes in interest rates used for margining, discounting, or contract price alignment as eligible for certain optional expedients and exceptions in Topic 848. Upon adoption of ASU 2021-01, Northern Trust elected the expedients provided in Topic 848 with no significant impact on Northern Trust’s consolidated balance sheets or consolidated statements of income.</span></div>
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	41155700000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	897600000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	31300000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	42022000000.0	USD
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
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	7508100000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	7598700000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	18696400000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	19076100000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	12334000000.0	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	12673300000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	2617200000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	2673900000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	41155700000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	42022000000.0	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	2995700000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	15300000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	3370900000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	16000000.0	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	6366600000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	31300000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	7850300000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	57000000.0	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	10615200000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	51600000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	18465500000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	108600000	USD
CY2020Q4	ntrs	Number Of Securities Unrealized Losses Position NumberOfSecuritiesUnrealizedLossesPosition	412	investment
CY2020Q4	ntrs	Securities Continuous Unrealized Loss Position Fair Value SecuritiesContinuousUnrealizedLossPositionFairValue	6400000000	USD
CY2020Q4	ntrs	Securities Continuous Unrealized Loss Position Aggregate Losses SecuritiesContinuousUnrealizedLossPositionAggregateLosses	31300000	USD
CY2020Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	17791100000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	84300000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	78000000.0	USD
CY2020Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	17797400000	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
CY2020Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	17800000000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue	76500000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	11593600000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	11603300000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	5607200000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	5660800000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount	473300000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	468100000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	117000000.0	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	65200000	USD
CY2020Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	17791100000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	17797400000	USD
CY2020	ntrs	Held To Maturity Securities Transferred From Available For Sale HeldToMaturitySecuritiesTransferredFromAvailableForSale	301500000	USD
CY2019	ntrs	Held To Maturity Securities Transferred From Available For Sale HeldToMaturitySecuritiesTransferredFromAvailableForSale	160800000	USD
CY2020Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	17791100000	USD
CY2020Q4	ntrs	Debt Securities Held To Maturity Percent Of Portfolio DebtSecuritiesHeldToMaturityPercentOfPortfolio	1
CY2020	ntrs	Proceeds From Sales Of Investment Securities ProceedsFromSalesOfInvestmentSecurities	879900000	USD
CY2019	ntrs	Proceeds From Sales Of Investment Securities ProceedsFromSalesOfInvestmentSecurities	1200000000	USD
CY2018	ntrs	Proceeds From Sales Of Investment Securities ProceedsFromSalesOfInvestmentSecurities	307300000	USD
CY2020	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	3400000	USD
CY2019	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	2400000	USD
CY2018	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	1500000	USD
CY2020	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	3800000	USD
CY2019	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	3500000	USD
CY2018	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	2000000.0	USD
CY2020	us-gaap	Other Than Temporary Impairment Loss Debt Securities Portion Recognized In Earnings OtherThanTemporaryImpairmentLossDebtSecuritiesPortionRecognizedInEarnings	0	USD
CY2019	us-gaap	Other Than Temporary Impairment Loss Debt Securities Portion Recognized In Earnings OtherThanTemporaryImpairmentLossDebtSecuritiesPortionRecognizedInEarnings	300000	USD
CY2018	us-gaap	Other Than Temporary Impairment Loss Debt Securities Portion Recognized In Earnings OtherThanTemporaryImpairmentLossDebtSecuritiesPortionRecognizedInEarnings	500000	USD
CY2020	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	-400000	USD
CY2019	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	-1400000	USD
CY2018	us-gaap	Realized Investment Gains Losses RealizedInvestmentGainsLosses	-1000000.0	USD
CY2020	us-gaap	Schedule Of Resale Agreements ScheduleOfResaleAgreements	<table style="border-collapse:collapse;display:inline-table;vertical-align:top;width:100.000%"><tr><td style="width:1.0%"/><td style="width:78.627%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:9.036%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:9.037%"/><td style="width:0.1%"/></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:7pt;font-weight:400;line-height:100%">($ In Millions)</span></td><td colspan="3" style="padding:2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:7pt;font-weight:700;line-height:100%">2020</span></td><td colspan="3" style="padding:2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:7pt;font-weight:400;line-height:100%">2019</span></td></tr><tr><td colspan="3" style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 1pt;text-align:left;vertical-align:top"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Balance at December 31</span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">1,596.5</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">707.8 </span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#ffffff;padding:2px 1pt;text-align:left;vertical-align:top"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Average Balance During the Year</span></td><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">1,253.1</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">835.0 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#cceeff;padding:2px 1pt;text-align:left;vertical-align:top"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Average Interest Rate Earned During the Year</span></td><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">0.31</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">%</span></td><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">2.10 </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">%</span></td></tr><tr><td colspan="3" style="background-color:#ffffff;padding:2px 1pt;text-align:left;vertical-align:top"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Maximum Month-End Balance During the Year</span></td><td style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">$</span></td><td style="background-color:#ffffff;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">2,055.6</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#ffffff;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">1,290.0 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr></table>
CY2020Q4	us-gaap	Securities Purchased Under Agreements To Resell SecuritiesPurchasedUnderAgreementsToResell	1596500000	USD
CY2019Q4	us-gaap	Securities Purchased Under Agreements To Resell SecuritiesPurchasedUnderAgreementsToResell	707800000	USD
CY2020	ntrs	Securities Purchased Under Agreement To Resell Average Balance During Period SecuritiesPurchasedUnderAgreementToResellAverageBalanceDuringPeriod	1253100000	USD
CY2019	ntrs	Securities Purchased Under Agreement To Resell Average Balance During Period SecuritiesPurchasedUnderAgreementToResellAverageBalanceDuringPeriod	835000000.0	USD
CY2020	ntrs	Securities Purchased Under Agreement To Resell Average Interest Rate Earned During Period SecuritiesPurchasedUnderAgreementToResellAverageInterestRateEarnedDuringPeriod	0.0031
CY2019	ntrs	Securities Purchased Under Agreement To Resell Average Interest Rate Earned During Period SecuritiesPurchasedUnderAgreementToResellAverageInterestRateEarnedDuringPeriod	0.0210
CY2020	ntrs	Securities Purchased Under Agreement To Resell Maximum Month End Balance During Period SecuritiesPurchasedUnderAgreementToResellMaximumMonthEndBalanceDuringPeriod	2055600000	USD
CY2019	ntrs	Securities Purchased Under Agreement To Resell Maximum Month End Balance During Period SecuritiesPurchasedUnderAgreementToResellMaximumMonthEndBalanceDuringPeriod	1290000000.0	USD
CY2020	us-gaap	Schedule Of Repurchase Agreements ScheduleOfRepurchaseAgreements	<table style="border-collapse:collapse;display:inline-table;vertical-align:top;width:100.000%"><tr><td style="width:1.0%"/><td style="width:78.627%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:9.036%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:9.037%"/><td style="width:0.1%"/></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:7pt;font-weight:400;line-height:100%">($ In Millions)</span></td><td colspan="3" style="padding:2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:7pt;font-weight:700;line-height:100%">2020</span></td><td colspan="3" style="padding:2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:7pt;font-weight:400;line-height:100%">2019</span></td></tr><tr><td colspan="3" style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 1pt;text-align:left;vertical-align:top"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Balance at December 31</span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">39.8</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">489.7 </span></td><td style="background-color:#cceeff;border-top:1pt solid #000000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#ffffff;padding:2px 1pt;text-align:left;vertical-align:top"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Average Balance During the Year</span></td><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">218.3</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">339.0 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#cceeff;padding:2px 1pt;text-align:left;vertical-align:top"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Average Interest Rate Paid During the Year</span></td><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">0.47</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">%</span></td><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">1.89 </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">%</span></td></tr><tr><td colspan="3" style="background-color:#ffffff;padding:2px 1pt;text-align:left;vertical-align:top"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Maximum Month-End Balance During the Year</span></td><td style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">$</span></td><td style="background-color:#ffffff;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">269.8</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#ffffff;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">489.7 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr></table>
CY2020Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	39800000	USD
CY2019Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	489700000	USD
CY2020	ntrs	Securities Sold Under Agreements To Repurchase Average Balance During Period SecuritiesSoldUnderAgreementsToRepurchaseAverageBalanceDuringPeriod	218300000	USD
CY2019	ntrs	Securities Sold Under Agreements To Repurchase Average Balance During Period SecuritiesSoldUnderAgreementsToRepurchaseAverageBalanceDuringPeriod	339000000.0	USD
CY2020	ntrs	Securities Sold Under Agreements To Repurchase Average Interest Rate Paid During Period SecuritiesSoldUnderAgreementsToRepurchaseAverageInterestRatePaidDuringPeriod	0.0047
CY2019	ntrs	Securities Sold Under Agreements To Repurchase Average Interest Rate Paid During Period SecuritiesSoldUnderAgreementsToRepurchaseAverageInterestRatePaidDuringPeriod	0.0189
CY2020	ntrs	Securities Sold Under Agreements To Repurchase Maximum Month End Balance During Period SecuritiesSoldUnderAgreementsToRepurchaseMaximumMonthEndBalanceDuringPeriod	269800000	USD
CY2019	ntrs	Securities Sold Under Agreements To Repurchase Maximum Month End Balance During Period SecuritiesSoldUnderAgreementsToRepurchaseMaximumMonthEndBalanceDuringPeriod	489700000	USD
CY2020Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	33759700000	USD
CY2019Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	31409600000	USD
CY2020	ntrs	Line Of Credit Draw Down Period LineOfCreditDrawDownPeriod	P10Y
CY2019Q4	ntrs	Loans Receivable Overdraft Advances LoansReceivableOverdraftAdvances	1100000000	USD
CY2020Q4	ntrs	Loans Receivable Overdraft Advances LoansReceivableOverdraftAdvances	1100000000	USD
CY2020Q4	ntrs	Overdrawn Demand Deposit Accounts OverdrawnDemandDepositAccounts	26400000	USD
CY2019Q4	ntrs	Overdrawn Demand Deposit Accounts OverdrawnDemandDepositAccounts	90400000	USD
CY2020Q4	us-gaap	Direct Financing Lease Lease Receivable DirectFinancingLeaseLeaseReceivable	0	USD
CY2019Q4	us-gaap	Direct Financing Lease Lease Receivable DirectFinancingLeaseLeaseReceivable	1500000	USD
CY2020Q4	us-gaap	Direct Financing Lease Unguaranteed Residual Asset DirectFinancingLeaseUnguaranteedResidualAsset	0	USD
CY2019Q4	us-gaap	Direct Financing Lease Unguaranteed Residual Asset DirectFinancingLeaseUnguaranteedResidualAsset	21300000	USD
CY2020Q4	ntrs	Direct Financing Lease Initial Direct Costs DirectFinancingLeaseInitialDirectCosts	0	USD
CY2019Q4	ntrs	Direct Financing Lease Initial Direct Costs DirectFinancingLeaseInitialDirectCosts	200000	USD
CY2020Q4	us-gaap	Direct Financing Lease Deferred Selling Profit DirectFinancingLeaseDeferredSellingProfit	0	USD
CY2019Q4	us-gaap	Direct Financing Lease Deferred Selling Profit DirectFinancingLeaseDeferredSellingProfit	0	USD
CY2020Q4	us-gaap	Direct Financing Lease Net Investment In Lease DirectFinancingLeaseNetInvestmentInLease	0	USD
CY2019Q4	us-gaap	Direct Financing Lease Net Investment In Lease DirectFinancingLeaseNetInvestmentInLease	23000000.0	USD
CY2020Q4	us-gaap	Leveraged Leases Net Investment In Leveraged Leases Disclosure Rental Receivables Net LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureRentalReceivablesNet	11800000	USD
CY2019Q4	us-gaap	Leveraged Leases Net Investment In Leveraged Leases Disclosure Rental Receivables Net LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureRentalReceivablesNet	19100000	USD
CY2020Q4	us-gaap	Leveraged Leases Net Investment In Leveraged Leases Disclosure Residual Value Of Leased Assets LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureResidualValueOfLeasedAssets	0	USD
CY2019Q4	us-gaap	Leveraged Leases Net Investment In Leveraged Leases Disclosure Residual Value Of Leased Assets LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureResidualValueOfLeasedAssets	33100000	USD
CY2020Q4	us-gaap	Leveraged Leases Net Investment In Leveraged Leases Disclosure Deferred Income LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureDeferredIncome	400000	USD
CY2019Q4	us-gaap	Leveraged Leases Net Investment In Leveraged Leases Disclosure Deferred Income LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureDeferredIncome	9600000	USD
CY2020Q4	us-gaap	Leveraged Leases Net Investment In Leveraged Leases Disclosure Investment In Leveraged Leases Net LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureInvestmentInLeveragedLeasesNet	11400000	USD
CY2019Q4	us-gaap	Leveraged Leases Net Investment In Leveraged Leases Disclosure Investment In Leveraged Leases Net LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureInvestmentInLeveragedLeasesNet	42600000	USD
CY2020Q4	us-gaap	Notes Receivable Net NotesReceivableNet	11400000	USD
CY2019Q4	us-gaap	Notes Receivable Net NotesReceivableNet	65600000	USD
CY2020Q4	us-gaap	Financing Receivable Originated In Current Fiscal Year FinancingReceivableOriginatedInCurrentFiscalYear	7448600000	USD
CY2020Q4	us-gaap	Financing Receivable Originated In Fiscal Year Before Latest Fiscal Year FinancingReceivableOriginatedInFiscalYearBeforeLatestFiscalYear	3667900000	USD
CY2020Q4	us-gaap	Financing Receivable Originated Two Years Before Latest Fiscal Year FinancingReceivableOriginatedTwoYearsBeforeLatestFiscalYear	1352600000	USD
CY2020Q4	us-gaap	Financing Receivable Originated Three Years Before Latest Fiscal Year FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear	1123100000	USD
CY2020Q4	us-gaap	Financing Receivable Originated Four Years Before Latest Fiscal Year FinancingReceivableOriginatedFourYearsBeforeLatestFiscalYear	1254800000	USD
CY2020Q4	us-gaap	Financing Receivable Originated Five Or More Years Before Latest Fiscal Year FinancingReceivableOriginatedFiveOrMoreYearsBeforeLatestFiscalYear	3128500000	USD
CY2020Q4	us-gaap	Financing Receivable Revolving FinancingReceivableRevolving	15453600000	USD
CY2020Q4	us-gaap	Financing Receivable Revolving Converted To Term Loan FinancingReceivableRevolvingConvertedToTermLoan	330600000	USD
CY2020Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	33759700000	USD
CY2020Q4	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	33395600000	USD
CY2020Q4	ntrs	Financing Receivable Accrual FinancingReceivableAccrual	33628000000.0	USD
CY2020Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	131700000	USD
CY2020Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	33759700000	USD
CY2020Q4	us-gaap	Financing Receivable Nonaccrual No Allowance FinancingReceivableNonaccrualNoAllowance	98100000	USD
CY2020Q4	us-gaap	Other Real Estate And Foreclosed Assets OtherRealEstateAndForeclosedAssets	700000	USD
CY2020Q4	ntrs	Financing Receivable Nonaccrual Including Other Real Estate Owned FinancingReceivableNonaccrualIncludingOtherRealEstateOwned	132400000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	31230600000	USD
CY2019Q4	ntrs	Financing Receivable Accrual FinancingReceivableAccrual	31326000000.0	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	83600000	USD
CY2019Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	31409600000	USD
CY2019Q4	us-gaap	Financing Receivable Nonaccrual No Allowance FinancingReceivableNonaccrualNoAllowance	70600000	USD
CY2019Q4	us-gaap	Other Real Estate And Foreclosed Assets OtherRealEstateAndForeclosedAssets	3200000	USD
CY2019Q4	ntrs	Financing Receivable Nonaccrual Including Other Real Estate Owned FinancingReceivableNonaccrualIncludingOtherRealEstateOwned	86800000	USD
CY2020	us-gaap	Financing Receivable Nonaccrual Interest Income FinancingReceivableNonaccrualInterestIncome	4600000	USD
CY2019	us-gaap	Financing Receivable Nonaccrual Interest Income FinancingReceivableNonaccrualInterestIncome	7300000	USD
CY2018	us-gaap	Financing Receivable Nonaccrual Interest Income FinancingReceivableNonaccrualInterestIncome	8000000.0	USD
CY2020Q4	ntrs	Financing Receivable Nonaccrual Troubled Debt Restructuring FinancingReceivableNonaccrualTroubledDebtRestructuring	38900000	USD
CY2019Q4	ntrs	Financing Receivable Nonaccrual Troubled Debt Restructuring FinancingReceivableNonaccrualTroubledDebtRestructuring	54900000	USD
CY2020Q4	us-gaap	Financing Receivable Modifications Recorded Investment FinancingReceivableModificationsRecordedInvestment	29300000	USD
CY2019Q4	us-gaap	Financing Receivable Modifications Recorded Investment FinancingReceivableModificationsRecordedInvestment	27700000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Impaired Commitment To Lend LoansAndLeasesReceivableImpairedCommitmentToLend	10400000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Impaired Commitment To Lend LoansAndLeasesReceivableImpairedCommitmentToLend	8200000	USD
CY2020	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	25	contract
CY2020	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	40500000	USD
CY2020	ntrs	Financing Receivable Troubled Debt Restructuring Postmodification Unpaid Principal Balance FinancingReceivableTroubledDebtRestructuringPostmodificationUnpaidPrincipalBalance	41200000	USD
CY2019	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	48	contract
CY2019	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	44900000	USD
CY2019	ntrs	Financing Receivable Troubled Debt Restructuring Postmodification Unpaid Principal Balance FinancingReceivableTroubledDebtRestructuringPostmodificationUnpaidPrincipalBalance	47600000	USD
CY2020	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	0	loan
CY2019	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	5	loan
CY2019Q4	us-gaap	Impaired Financing Receivable Recorded Investment ImpairedFinancingReceivableRecordedInvestment	5800000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Unpaid Principal Balance ImpairedFinancingReceivableUnpaidPrincipalBalance	6100000	USD
CY2020Q4	us-gaap	Other Real Estate And Foreclosed Assets OtherRealEstateAndForeclosedAssets	700000	USD
CY2019Q4	us-gaap	Other Real Estate And Foreclosed Assets OtherRealEstateAndForeclosedAssets	3200000	USD
CY2020Q4	us-gaap	Mortgage Loans In Process Of Foreclosure Amount MortgageLoansInProcessOfForeclosureAmount	7900000	USD
CY2019Q4	us-gaap	Mortgage Loans In Process Of Foreclosure Amount MortgageLoansInProcessOfForeclosureAmount	18100000	USD
CY2020	ntrs	Financing Receivable Credit Loss Estimate Time Period FinancingReceivableCreditLossEstimateTimePeriod	P2Y
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	104500000	USD
CY2019Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	19900000	USD
CY2019Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	0	USD
CY2019Q4	ntrs	Other Financial Assets Allowance For Credit Loss OtherFinancialAssetsAllowanceForCreditLoss	0	USD
CY2019Q4	ntrs	Allowance For Credit Loss AllowanceForCreditLoss	124400000	USD
CY2020	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	9700000	USD
CY2020	ntrs	Off Balance Sheet Allowance For Credit Loss Writeoff OffBalanceSheetAllowanceForCreditLossWriteoff	0	USD
CY2020	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Writeoff DebtSecuritiesHeldToMaturityAllowanceForCreditLossWriteoff	0	USD
CY2020	ntrs	Other Financial Assets Allowance For Credit Loss Writeoff OtherFinancialAssetsAllowanceForCreditLossWriteoff	0	USD
CY2020	ntrs	Allowance For Credit Loss Writeoff AllowanceForCreditLossWriteoff	9700000	USD
CY2020	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	6500000	USD
CY2020	ntrs	Off Balance Sheet Credit Loss Liability Recovery OffBalanceSheetCreditLossLiabilityRecovery	0	USD
CY2020	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Recovery DebtSecuritiesHeldToMaturityAllowanceForCreditLossRecovery	0	USD
CY2020	ntrs	Other Financial Assets Allowance For Credit Loss Recovery OtherFinancialAssetsAllowanceForCreditLossRecovery	0	USD
CY2020	ntrs	Allowance For Credit Loss Recovery AllowanceForCreditLossRecovery	6500000	USD
CY2020	us-gaap	Financing Receivable Allowance For Credit Loss Writeoff After Recovery FinancingReceivableAllowanceForCreditLossWriteoffAfterRecovery	3200000	USD
CY2020	ntrs	Off Balance Sheet Credit Loss Liability Changein Present Value Expense Reversal OffBalanceSheetCreditLossLiabilityChangeinPresentValueExpenseReversal	0	USD
CY2020	us-gaap	Debt Securities Held To Maturity Change In Present Value Expense Reversal DebtSecuritiesHeldToMaturityChangeInPresentValueExpenseReversal	0	USD
CY2020	ntrs	Other Financial Assets Change In Present Value Expense Reversal OtherFinancialAssetsChangeInPresentValueExpenseReversal	0	USD
CY2020	ntrs	Change In Present Expense Reversal And Writeoff After Recovery ChangeInPresentExpenseReversalAndWriteoffAfterRecovery	3200000	USD
CY2020	us-gaap	Provision For Loan Losses Expensed ProvisionForLoanLossesExpensed	91600000	USD
CY2020	us-gaap	Off Balance Sheet Credit Loss Liability Credit Loss Expense Reversal OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal	32300000	USD
CY2020	us-gaap	Debt Securities Held To Maturity Credit Loss Expense Reversal DebtSecuritiesHeldToMaturityCreditLossExpenseReversal	700000	USD
CY2020	ntrs	Other Financial Assets Credit Loss Expense Reversal OtherFinancialAssetsCreditLossExpenseReversal	400000	USD
CY2020	ntrs	Credit Loss Expense Reversal CreditLossExpenseReversal	125000000.0	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	190700000	USD
CY2020Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	61100000	USD
CY2020Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	7300000	USD
CY2020Q4	ntrs	Other Financial Assets Allowance For Credit Loss OtherFinancialAssetsAllowanceForCreditLoss	800000	USD
CY2020Q4	ntrs	Allowance For Credit Loss AllowanceForCreditLoss	259900000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	112600000	USD
CY2018Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	25600000	USD
CY2018Q4	ntrs	Allowance For Credit Loss AllowanceForCreditLoss	138200000	USD
CY2019	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	6500000	USD
CY2019	ntrs	Off Balance Sheet Allowance For Credit Loss Writeoff OffBalanceSheetAllowanceForCreditLossWriteoff	0	USD
CY2019	ntrs	Allowance For Credit Loss Writeoff AllowanceForCreditLossWriteoff	6500000	USD
CY2019	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	7200000	USD
CY2019	ntrs	Off Balance Sheet Credit Loss Liability Recovery OffBalanceSheetCreditLossLiabilityRecovery	0	USD
CY2019	ntrs	Allowance For Credit Loss Recovery AllowanceForCreditLossRecovery	7200000	USD
CY2019	us-gaap	Financing Receivable Allowance For Credit Loss Writeoff After Recovery FinancingReceivableAllowanceForCreditLossWriteoffAfterRecovery	-700000	USD
CY2019	ntrs	Off Balance Sheet Credit Loss Liability Changein Present Value Expense Reversal OffBalanceSheetCreditLossLiabilityChangeinPresentValueExpenseReversal	0	USD
CY2019	us-gaap	Financing Receivable Allowance For Credit Loss Writeoff After Recovery FinancingReceivableAllowanceForCreditLossWriteoffAfterRecovery	-700000	USD
CY2019	us-gaap	Provision For Loan Losses Expensed ProvisionForLoanLossesExpensed	-8800000	USD
CY2019	us-gaap	Off Balance Sheet Credit Loss Liability Credit Loss Expense Reversal OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal	-5700000	USD
CY2019	ntrs	Credit Loss Expense Reversal CreditLossExpenseReversal	-14500000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	104500000	USD
CY2019Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	19900000	USD
CY2019Q4	ntrs	Allowance For Credit Loss AllowanceForCreditLoss	124400000	USD
CY2017Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	131200000	USD
CY2017Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	22600000	USD
CY2017Q4	ntrs	Allowance For Credit Loss AllowanceForCreditLoss	153800000	USD
CY2018	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	10100000	USD
CY2018	ntrs	Off Balance Sheet Allowance For Credit Loss Writeoff OffBalanceSheetAllowanceForCreditLossWriteoff	0	USD
CY2018	ntrs	Allowance For Credit Loss Writeoff AllowanceForCreditLossWriteoff	10100000	USD
CY2018	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	9000000.0	USD
CY2018	ntrs	Off Balance Sheet Credit Loss Liability Recovery OffBalanceSheetCreditLossLiabilityRecovery	0	USD
CY2018	ntrs	Allowance For Credit Loss Recovery AllowanceForCreditLossRecovery	9000000.0	USD
CY2018	us-gaap	Financing Receivable Allowance For Credit Loss Writeoff After Recovery FinancingReceivableAllowanceForCreditLossWriteoffAfterRecovery	1100000	USD
CY2018	ntrs	Off Balance Sheet Credit Loss Liability Changein Present Value Expense Reversal OffBalanceSheetCreditLossLiabilityChangeinPresentValueExpenseReversal	0	USD
CY2018	us-gaap	Financing Receivable Allowance For Credit Loss Writeoff After Recovery FinancingReceivableAllowanceForCreditLossWriteoffAfterRecovery	1100000	USD
CY2018	us-gaap	Provision For Loan Losses Expensed ProvisionForLoanLossesExpensed	-17500000	USD
CY2018	us-gaap	Off Balance Sheet Credit Loss Liability Credit Loss Expense Reversal OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal	3000000.0	USD
CY2018	ntrs	Credit Loss Expense Reversal CreditLossExpenseReversal	-14500000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	112600000	USD
CY2018Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	25600000	USD
CY2018Q4	ntrs	Allowance For Credit Loss AllowanceForCreditLoss	138200000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	104500000	USD
CY2019Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	19900000	USD
CY2020	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	9700000	USD
CY2020	ntrs	Off Balance Sheet Allowance For Credit Loss Writeoff OffBalanceSheetAllowanceForCreditLossWriteoff	0	USD
CY2020	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	6500000	USD
CY2020	ntrs	Off Balance Sheet Credit Loss Liability Recovery OffBalanceSheetCreditLossLiabilityRecovery	0	USD
CY2020	us-gaap	Financing Receivable Allowance For Credit Loss Writeoff After Recovery FinancingReceivableAllowanceForCreditLossWriteoffAfterRecovery	3200000	USD
CY2020	ntrs	Off Balance Sheet Credit Loss Liability Changein Present Value Expense Reversal OffBalanceSheetCreditLossLiabilityChangeinPresentValueExpenseReversal	0	USD
CY2020	us-gaap	Provision For Loan Losses Expensed ProvisionForLoanLossesExpensed	91600000	USD
CY2020	us-gaap	Off Balance Sheet Credit Loss Liability Credit Loss Expense Reversal OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal	32300000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	190700000	USD
CY2020Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	61100000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	112600000	USD
CY2018Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	25600000	USD
CY2019	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	6500000	USD
CY2019	ntrs	Off Balance Sheet Allowance For Credit Loss Writeoff OffBalanceSheetAllowanceForCreditLossWriteoff	0	USD
CY2019	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	7200000	USD
CY2019	ntrs	Off Balance Sheet Credit Loss Liability Recovery OffBalanceSheetCreditLossLiabilityRecovery	0	USD
CY2019	us-gaap	Financing Receivable Allowance For Credit Loss Writeoff After Recovery FinancingReceivableAllowanceForCreditLossWriteoffAfterRecovery	-700000	USD
CY2019	ntrs	Off Balance Sheet Credit Loss Liability Changein Present Value Expense Reversal OffBalanceSheetCreditLossLiabilityChangeinPresentValueExpenseReversal	0	USD
CY2019	us-gaap	Provision For Loan Losses Expensed ProvisionForLoanLossesExpensed	-8800000	USD
CY2019	us-gaap	Off Balance Sheet Credit Loss Liability Credit Loss Expense Reversal OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal	-5700000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	104500000	USD
CY2019Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	19900000	USD
CY2019Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	31409600000	USD
CY2017Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	131200000	USD
CY2017Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	22600000	USD
CY2018	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	10100000	USD
CY2018	ntrs	Off Balance Sheet Allowance For Credit Loss Writeoff OffBalanceSheetAllowanceForCreditLossWriteoff	0	USD
CY2018	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	9000000.0	USD
CY2018	ntrs	Off Balance Sheet Credit Loss Liability Recovery OffBalanceSheetCreditLossLiabilityRecovery	0	USD
CY2018	us-gaap	Financing Receivable Allowance For Credit Loss Writeoff After Recovery FinancingReceivableAllowanceForCreditLossWriteoffAfterRecovery	1100000	USD
CY2018	ntrs	Off Balance Sheet Credit Loss Liability Changein Present Value Expense Reversal OffBalanceSheetCreditLossLiabilityChangeinPresentValueExpenseReversal	0	USD
CY2018	us-gaap	Provision For Loan Losses Expensed ProvisionForLoanLossesExpensed	-17500000	USD
CY2018	us-gaap	Off Balance Sheet Credit Loss Liability Credit Loss Expense Reversal OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal	3000000.0	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	112600000	USD
CY2018Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	25600000	USD
CY2020Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	131700000	USD
CY2019Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	92200000	USD
CY2020Q4	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	33628000000.0	USD
CY2019Q4	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	31317400000	USD
CY2020Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	33759700000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	9100000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	5000000.0	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	181600000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	99500000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	190700000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	104500000	USD
CY2020Q4	ntrs	Off Balance Sheet Credit Loss Liability Individually Evaluated For Impairment OffBalanceSheetCreditLossLiabilityIndividuallyEvaluatedForImpairment	1600000	USD
CY2019Q4	ntrs	Off Balance Sheet Credit Loss Liability Individually Evaluated For Impairment OffBalanceSheetCreditLossLiabilityIndividuallyEvaluatedForImpairment	1900000	USD
CY2020Q4	ntrs	Off Balance Sheet Credit Loss Liability Collectively Evaluated For Impairment OffBalanceSheetCreditLossLiabilityCollectivelyEvaluatedForImpairment	59500000	USD
CY2019Q4	ntrs	Off Balance Sheet Credit Loss Liability Collectively Evaluated For Impairment OffBalanceSheetCreditLossLiabilityCollectivelyEvaluatedForImpairment	18000000.0	USD
CY2020Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	61100000	USD
CY2019Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	19900000	USD
CY2020Q4	ntrs	Financing Receivable Allowance For Credit Losses And Off Balance Sheet Credit Loss Liability FinancingReceivableAllowanceForCreditLossesAndOffBalanceSheetCreditLossLiability	251800000	USD
CY2019Q4	ntrs	Financing Receivable Allowance For Credit Losses And Off Balance Sheet Credit Loss Liability FinancingReceivableAllowanceForCreditLossesAndOffBalanceSheetCreditLossLiability	124400000	USD
CY2019Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	0	USD
CY2020	us-gaap	Debt Securities Held To Maturity Credit Loss Expense Reversal DebtSecuritiesHeldToMaturityCreditLossExpenseReversal	700000	USD
CY2020Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	7300000	USD
CY2020Q1	us-gaap	Other Than Temporary Impairment Loss Debt Securities Portion Recognized In Earnings OtherThanTemporaryImpairmentLossDebtSecuritiesPortionRecognizedInEarnings	4400000	USD
CY2020Q4	ntrs	Other Financial Assets Allowance For Credit Loss OtherFinancialAssetsAllowanceForCreditLoss	800000	USD
CY2020Q4	us-gaap	Financing Receivable Accrued Interest After Allowance For Credit Loss FinancingReceivableAccruedInterestAfterAllowanceForCreditLoss	55300000	USD
CY2019Q4	us-gaap	Financing Receivable Accrued Interest After Allowance For Credit Loss FinancingReceivableAccruedInterestAfterAllowanceForCreditLoss	84500000	USD
CY2020Q4	us-gaap	Debt Securities Held To Maturity Accrued Interest After Allowance For Credit Loss DebtSecuritiesHeldToMaturityAccruedInterestAfterAllowanceForCreditLoss	73800000	USD
CY2019Q4	us-gaap	Debt Securities Held To Maturity Accrued Interest After Allowance For Credit Loss DebtSecuritiesHeldToMaturityAccruedInterestAfterAllowanceForCreditLoss	82300000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Accrued Interest After Allowance For Credit Loss DebtSecuritiesAvailableForSaleAccruedInterestAfterAllowanceForCreditLoss	106300000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Accrued Interest After Allowance For Credit Loss DebtSecuritiesAvailableForSaleAccruedInterestAfterAllowanceForCreditLoss	119000000.0	USD
CY2020Q4	ntrs	Other Financial Assets Accrued Interest After Allowance For Credit Loss OtherFinancialAssetsAccruedInterestAfterAllowanceForCreditLoss	1400000	USD
CY2019Q4	ntrs	Other Financial Assets Accrued Interest After Allowance For Credit Loss OtherFinancialAssetsAccruedInterestAfterAllowanceForCreditLoss	14700000	USD
CY2020Q4	ntrs	Credit Risk To Banks Non Interest Bearing Balances Held At Banks CreditRiskToBanksNonInterestBearingBalancesHeldAtBanks	4400000000	USD
CY2020Q4	ntrs	Credit Risk To Banks CreditRiskToBanks	4300000000	USD
CY2020Q4	us-gaap	Federal Funds Sold And Securities Purchased Under Agreements To Resell FederalFundsSoldAndSecuritiesPurchasedUnderAgreementsToResell	1600000000	USD
CY2019Q4	ntrs	Credit Risk To Banks Non Interest Bearing Balances Held At Banks CreditRiskToBanksNonInterestBearingBalancesHeldAtBanks	4900000000	USD
CY2019Q4	ntrs	Credit Risk To Banks CreditRiskToBanks	4300000000	USD
CY2019Q4	us-gaap	Securities Purchased Under Agreements To Resell SecuritiesPurchasedUnderAgreementsToResell	707800000	USD
CY2019Q4	us-gaap	Federal Funds Sold FederalFundsSold	5000000.0	USD
CY2020Q4	ntrs	Loans And Leases Receivable Residential Real Estate LoansAndLeasesReceivableResidentialRealEstate	6000000000.0	USD
CY2019Q4	ntrs	Loans And Leases Receivable Residential Real Estate LoansAndLeasesReceivableResidentialRealEstate	6000000000.0	USD
CY2020Q4	ntrs	Residential Real Estate Loans Percentage Of Total Us Loansand Leases ResidentialRealEstateLoansPercentageOfTotalUSLoansandLeases	0.19
CY2019Q4	ntrs	Residential Real Estate Loans Percentage Of Total Us Loansand Leases ResidentialRealEstateLoansPercentageOfTotalUSLoansandLeases	0.20
CY2020Q4	ntrs	Loans And Leases Receivable Residential Real Estate LoansAndLeasesReceivableResidentialRealEstate	6000000000.0	USD
CY2020Q4	ntrs	Commitments To Extend Credit CommitmentsToExtendCredit	676100000	USD
CY2019Q4	ntrs	Commitments To Extend Credit CommitmentsToExtendCredit	714200000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	1612600000	USD
CY2020Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	1097700000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	514900000	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
CY2020	us-gaap	Depreciation Nonproduction DepreciationNonproduction	116500000	USD
CY2019	us-gaap	Depreciation Nonproduction DepreciationNonproduction	103200000	USD
CY2018	us-gaap	Depreciation Nonproduction DepreciationNonproduction	108600000	USD
CY2020	us-gaap	Operating Lease Cost OperatingLeaseCost	119400000	USD
CY2019	us-gaap	Operating Lease Cost OperatingLeaseCost	102200000	USD
CY2020	us-gaap	Variable Lease Cost VariableLeaseCost	32700000	USD
CY2019	us-gaap	Variable Lease Cost VariableLeaseCost	38700000	USD
CY2020	us-gaap	Sublease Income SubleaseIncome	4800000	USD
CY2019	us-gaap	Sublease Income SubleaseIncome	6600000	USD
CY2020	us-gaap	Lease Cost LeaseCost	147300000	USD
CY2019	us-gaap	Lease Cost LeaseCost	134300000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	99100000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	92600000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	85600000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	74700000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	77000000.0	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	372500000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	801500000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	100900000	USD
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	700600000	USD
CY2020Q4	ntrs	Lessee Operating Lease Lease Notyet Commenced Liability LesseeOperatingLeaseLeaseNotyetCommencedLiability	32300000	USD
CY2020Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	560500000	USD
CY2019Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	491600000	USD
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	700600000	USD
CY2019Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	603100000	USD
CY2020Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P10Y
CY2019Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P9Y2M12D
CY2020Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.025
CY2019Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.030
CY2020	us-gaap	Operating Lease Payments OperatingLeasePayments	107900000	USD
CY2019	us-gaap	Operating Lease Payments OperatingLeasePayments	101200000	USD
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	164800000	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	108300000	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
CY2020	us-gaap	Goodwill Foreign Currency Translation Gain Loss GoodwillForeignCurrencyTranslationGainLoss	10400000	USD
CY2020Q4	us-gaap	Goodwill Goodwill	707200000	USD
CY2020Q4	ntrs	Contractual Maturities Time Deposits250000 Or More Next Twelve Months ContractualMaturitiesTimeDeposits250000OrMoreNextTwelveMonths	865600000	USD
CY2020Q4	ntrs	Contractual Maturities Time Deposits250000 Or More Year Two ContractualMaturitiesTimeDeposits250000OrMoreYearTwo	36100000	USD
CY2020Q4	ntrs	Contractual Maturities Time Deposits250000 Or More Year Three ContractualMaturitiesTimeDeposits250000OrMoreYearThree	3100000	USD
CY2020Q4	ntrs	Contractual Maturities Time Deposits250000 Or More Year Four ContractualMaturitiesTimeDeposits250000OrMoreYearFour	1200000	USD
CY2020Q4	ntrs	Contractual Maturities Time Deposits250000 Or More Year Five ContractualMaturitiesTimeDeposits250000OrMoreYearFive	300000	USD
CY2020Q4	ntrs	Contractual Maturities Time Deposits250000 Or More After Year Five ContractualMaturitiesTimeDeposits250000OrMoreAfterYearFive	500000	USD
CY2020Q4	ntrs	Time Deposits250000 Or More TimeDeposits250000OrMore	906800000	USD
CY2019Q4	us-gaap	Time Deposits At Or Above Fdic Insurance Limit TimeDepositsAtOrAboveFDICInsuranceLimit	1700000000	USD
CY2019Q4	us-gaap	Interest Bearing Domestic Deposit Certificates Of Deposits InterestBearingDomesticDepositCertificatesOfDeposits	711400000	USD
CY2019Q4	us-gaap	Deposits Foreign DepositsForeign	1000000000.0	USD
CY2020Q4	us-gaap	Senior Notes SeniorNotes	3122400000	USD
CY2019Q4	us-gaap	Senior Notes SeniorNotes	2573000000.0	USD
CY2020Q4	ntrs	Long Term Debt Qualifying As Risk Based Capital LongTermDebtQualifyingAsRiskBasedCapital	949700000	USD
CY2019Q4	ntrs	Long Term Debt Qualifying As Risk Based Capital LongTermDebtQualifyingAsRiskBasedCapital	1099500000	USD
CY2020	us-gaap	Debt Instrument Redemption Price Percentage DebtInstrumentRedemptionPricePercentage	1
CY2020Q4	ntrs	Percentageof Securities Eligiblefor Tier2 Capital Treatment PercentageofSecuritiesEligibleforTier2CapitalTreatment	0.20
CY2020Q4	ntrs	Securities Eligiblefor Tier2 Capital Treatment Decline Rate SecuritiesEligibleforTier2CapitalTreatmentDeclineRate	0.10
CY2020Q4	ntrs	Debt Instrument Liquidation Amount Per Share DebtInstrumentLiquidationAmountPerShare	1000
CY2020Q4	ntrs	Trust Preferred Securities TrustPreferredSecurities	277800000	USD
CY2019Q4	ntrs	Trust Preferred Securities TrustPreferredSecurities	277700000	USD
CY2020Q4	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
CY2020	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	3276589	shares
CY2020	ntrs	Treasury Stock Sharebased Compensation Shares Acquired TreasuryStockSharebasedCompensationSharesAcquired	532713	shares
CY2020	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	299800000	USD
CY2020	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	91.49
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
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
CY2020	us-gaap	Stock Issued During Period Shares Share Based Compensation StockIssuedDuringPeriodSharesShareBasedCompensation	1512035	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
CY2020	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	344686	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
CY2020	us-gaap	Stock Redeemed Or Called During Period Shares StockRedeemedOrCalledDuringPeriodShares	3276589	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
CY2020Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	208289178	shares
CY2019Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	209709046	shares
CY2018Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	219012050	shares
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
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	622700000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Before Tax Portion Attributable To Parent OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent	790800000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Tax Portion Attributable To Parent1 OtherComprehensiveIncomeLossTaxPortionAttributableToParent1	168100000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	622700000	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
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	208319412	shares
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
CY2020	us-gaap	Net Income Loss NetIncomeLoss	1209300000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	1492200000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	1556400000	USD
CY2020	us-gaap	Preferred Stock Dividends Income Statement Impact PreferredStockDividendsIncomeStatementImpact	56200000	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
CY2020	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	1153100000	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
CY2020	us-gaap	Undistributed Earnings Loss Allocated To Participating Securities Basic UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic	12100000	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
CY2020	ntrs	Net Income Loss Allocated To Common Stockholders Basic NetIncomeLossAllocatedToCommonStockholdersBasic	1141000000.0	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
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	5.48
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	6.66
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	6.68
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	208319412	shares
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
CY2020	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	688574	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
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	209007986	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
CY2020	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	1141100000	USD
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
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	5.46
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	6.63
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	6.64
CY2020	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
CY2019	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
CY2018	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	3995000000.0	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
CY2020	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	290400000	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
CY2020	ntrs	Treasury Management Fees TreasuryManagementFees	45400000	USD
CY2019	ntrs	Treasury Management Fees TreasuryManagementFees	44500000	USD
CY2018	ntrs	Treasury Management Fees TreasuryManagementFees	51800000	USD
CY2020	ntrs	Security Commissionsand Trading Income SecurityCommissionsandTradingIncome	133200000	USD
CY2019	ntrs	Security Commissionsand Trading Income SecurityCommissionsandTradingIncome	103600000	USD
CY2018	ntrs	Security Commissionsand Trading Income SecurityCommissionsandTradingIncome	98300000	USD
CY2020	us-gaap	Other Operating Income OtherOperatingIncome	194000000.0	USD
CY2019	us-gaap	Other Operating Income OtherOperatingIncome	145500000	USD
CY2018	us-gaap	Other Operating Income OtherOperatingIncome	127500000	USD
CY2020	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-400000	USD
CY2019	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1400000	USD
CY2018	us-gaap	Marketable Securities Gain Loss MarketableSecuritiesGainLoss	-1000000.0	USD
CY2020	ntrs	Other Noninterest Income OtherNoninterestIncome	662600000	USD
CY2019	ntrs	Other Noninterest Income OtherNoninterestIncome	543100000	USD
CY2018	ntrs	Other Noninterest Income OtherNoninterestIncome	583800000	USD
CY2020	us-gaap	Noninterest Income NoninterestIncome	4657600000	USD
CY2019	us-gaap	Noninterest Income NoninterestIncome	4395200000	USD
CY2018	us-gaap	Noninterest Income NoninterestIncome	4337500000	USD
CY2020	ntrs	Security Commissionsand Trading Income SecurityCommissionsandTradingIncome	133200000	USD
CY2020	us-gaap	Other Operating Income OtherOperatingIncome	194000000.0	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
CY2020Q4	us-gaap	Contract With Customer Asset Net ContractWithCustomerAssetNet	935800000	USD
CY2019Q4	us-gaap	Contract With Customer Asset Net ContractWithCustomerAssetNet	903000000.0	USD
CY2020	us-gaap	Interest And Fee Income Loans And Leases InterestAndFeeIncomeLoansAndLeases	774600000	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
CY2020	us-gaap	Interest Income Securities Taxable InterestIncomeSecuritiesTaxable	812400000	USD
CY2019	us-gaap	Interest Income Securities Taxable InterestIncomeSecuritiesTaxable	1070700000	USD
CY2018	us-gaap	Interest Income Securities Taxable InterestIncomeSecuritiesTaxable	905200000	USD
CY2020	us-gaap	Interest Income Securities Tax Exempt InterestIncomeSecuritiesTaxExempt	1400000	USD
CY2019	us-gaap	Interest Income Securities Tax Exempt InterestIncomeSecuritiesTaxExempt	3800000	USD
CY2018	us-gaap	Interest Income Securities Tax Exempt InterestIncomeSecuritiesTaxExempt	7000000.0	USD
CY2020	us-gaap	Interest Income Deposits With Financial Institutions InterestIncomeDepositsWithFinancialInstitutions	22400000	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
CY2020	ntrs	Interest Income Federal Reserve Deposits And Other InterestIncomeFederalReserveDepositsAndOther	32700000	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
CY2020	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	1643500000	USD
CY2019	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	2499900000	USD
CY2018	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	2321400000	USD
CY2020	us-gaap	Interest Expense Deposits InterestExpenseDeposits	48400000	USD
CY2019	us-gaap	Interest Expense Deposits InterestExpenseDeposits	488900000	USD
CY2018	us-gaap	Interest Expense Deposits InterestExpenseDeposits	384600000	USD
CY2020	us-gaap	Interest Expense Federal Funds Purchased InterestExpenseFederalFundsPurchased	2200000	USD
CY2019	us-gaap	Interest Expense Federal Funds Purchased InterestExpenseFederalFundsPurchased	25900000	USD
CY2018	us-gaap	Interest Expense Federal Funds Purchased InterestExpenseFederalFundsPurchased	50300000	USD
CY2020	us-gaap	Interest Expense Securities Sold Under Agreements To Repurchase InterestExpenseSecuritiesSoldUnderAgreementsToRepurchase	1000000.0	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
CY2020	us-gaap	Interest Expense Other Short Term Borrowings InterestExpenseOtherShortTermBorrowings	45300000	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
CY2020	ntrs	Interest Expense Senior Notes InterestExpenseSeniorNotes	72700000	USD
CY2019	ntrs	Interest Expense Senior Notes InterestExpenseSeniorNotes	72600000	USD
CY2018	ntrs	Interest Expense Senior Notes InterestExpenseSeniorNotes	53400000	USD
CY2020	us-gaap	Interest Expense Other Long Term Debt InterestExpenseOtherLongTermDebt	26500000	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
CY2020	us-gaap	Interest Expense Junior Subordinated Debentures InterestExpenseJuniorSubordinatedDebentures	4200000	USD
CY2019	us-gaap	Interest Expense Junior Subordinated Debentures InterestExpenseJuniorSubordinatedDebentures	8200000	USD
CY2018	us-gaap	Interest Expense Junior Subordinated Debentures InterestExpenseJuniorSubordinatedDebentures	7500000	USD
CY2020	us-gaap	Interest Expense InterestExpense	200300000	USD
CY2019	us-gaap	Interest Expense InterestExpense	822000000.0	USD
CY2018	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	98300000	USD
CY2018	us-gaap	Interest Expense InterestExpense	698700000	USD
CY2020	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	1443200000	USD
CY2019	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	1677900000	USD
CY2018	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	1622700000	USD
CY2020	us-gaap	Other Operating Income OtherOperatingIncome	194000000.0	USD
CY2019	us-gaap	Other Operating Income OtherOperatingIncome	145500000	USD
CY2018	us-gaap	Other Operating Income OtherOperatingIncome	127500000	USD
CY2020	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	59200000	USD
CY2019	us-gaap	Marketing And Advertising Expense MarketingAndAdvertisingExpense	104200000	USD
CY2020	us-gaap	Other Labor Related Expenses OtherLaborRelatedExpenses	29400000	USD
CY2019	us-gaap	Other Labor Related Expenses OtherLaborRelatedExpenses	42800000	USD
CY2018	us-gaap	Other Labor Related Expenses OtherLaborRelatedExpenses	33600000	USD
CY2020	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	11800000	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
CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	16900000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	16600000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	17400000	USD
CY2020	ntrs	Noninterest Expense Other NoninterestExpenseOther	229400000	USD
CY2019	ntrs	Noninterest Expense Other NoninterestExpenseOther	156300000	USD
CY2018	ntrs	Noninterest Expense Other NoninterestExpenseOther	153900000	USD
CY2020	us-gaap	Other Noninterest Expense OtherNoninterestExpense	346700000	USD
CY2019	us-gaap	Other Noninterest Expense OtherNoninterestExpense	329800000	USD
CY2018	us-gaap	Other Noninterest Expense OtherNoninterestExpense	330600000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits EffectiveIncomeTaxRateReconciliationTaxCredits	0.010
CY2020	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
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
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Tax Exempt Income EffectiveIncomeTaxRateReconciliationTaxExemptIncome	0.009
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Tax Exempt Income EffectiveIncomeTaxRateReconciliationTaxExemptIncome	0.006
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Tax Exempt Income EffectiveIncomeTaxRateReconciliationTaxExemptIncome	0.004
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Foreign Income Tax Rate Differential EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential	0.007
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Foreign Income Tax Rate Differential EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential	0.002
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Foreign Income Tax Rate Differential EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential	-0.004
CY2020	ntrs	Income Tax Reconciliation Leveraged Lease Adjustments IncomeTaxReconciliationLeveragedLeaseAdjustments	-0.006
CY2019	ntrs	Income Tax Reconciliation Leveraged Lease Adjustments IncomeTaxReconciliationLeveragedLeaseAdjustments	-0.009
CY2018	ntrs	Income Tax Reconciliation Leveraged Lease Adjustments IncomeTaxReconciliationLeveragedLeaseAdjustments	-0.009
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits EffectiveIncomeTaxRateReconciliationTaxCredits	0.017
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits EffectiveIncomeTaxRateReconciliationTaxCredits	0.011
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Prior Year Income Taxes EffectiveIncomeTaxRateReconciliationPriorYearIncomeTaxes	0.016
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Prior Year Income Taxes EffectiveIncomeTaxRateReconciliationPriorYearIncomeTaxes	0
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Prior Year Income Taxes EffectiveIncomeTaxRateReconciliationPriorYearIncomeTaxes	0
CY2020	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.032
CY2019	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.028
CY2018	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.034
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Tax Cuts And Jobs Act Of2017 Percent EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActOf2017Percent	0
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Tax Cuts And Jobs Act Of2017 Percent EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActOf2017Percent	0
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Tax Cuts And Jobs Act Of2017 Percent EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActOf2017Percent	-0.002
CY2020	ntrs	Effective Income Tax Rate Reconciliation Effect Of Change In Accounting Method Percent EffectiveIncomeTaxRateReconciliationEffectOfChangeInAccountingMethodPercent	0
CY2019	ntrs	Effective Income Tax Rate Reconciliation Effect Of Change In Accounting Method Percent EffectiveIncomeTaxRateReconciliationEffectOfChangeInAccountingMethodPercent	0
CY2018	ntrs	Effective Income Tax Rate Reconciliation Effect Of Change In Accounting Method Percent EffectiveIncomeTaxRateReconciliationEffectOfChangeInAccountingMethodPercent	-0.012
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Change In Deferred Tax Assets Valuation Allowance EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance	0.016
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Change In Deferred Tax Assets Valuation Allowance EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance	0.015
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Change In Deferred Tax Assets Valuation Allowance EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance	0
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.008
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.002
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.003
CY2020	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.257
CY2019	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.232
CY2018	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.205
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	418300000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	451900000	USD
CY2020	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.257
CY2019	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.232
CY2020	us-gaap	Income Tax Reconciliation Prior Year Income Taxes IncomeTaxReconciliationPriorYearIncomeTaxes	26800000	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	22400000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	25300000	USD
CY2020Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	20700000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	22700000	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
CY2020	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	900000	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
CY2020	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	400000	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
CY2020	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	4200000	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
CY2020	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	0	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
CY2020Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	22400000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	25300000	USD
CY2019	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	150500000	USD
CY2018	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	162700000	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	21900000	USD
CY2020	us-gaap	Income Tax Examination Penalties And Interest Expense IncomeTaxExaminationPenaltiesAndInterestExpense	1200000	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
CY2020Q4	us-gaap	Income Tax Examination Penalties And Interest Accrued IncomeTaxExaminationPenaltiesAndInterestAccrued	9600000	USD
CY2019Q4	us-gaap	Income Tax Examination Penalties And Interest Accrued IncomeTaxExaminationPenaltiesAndInterestAccrued	8400000	USD
CY2020	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	203000000.0	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	216400000	USD
CY2018	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	132800000	USD
CY2020	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	57200000	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
CY2020	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	141700000	USD
CY2020	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	401900000	USD
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	417600000	USD
CY2018	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	390900000	USD
CY2020	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	8800000	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
CY2020	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	5400000	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
CY2020	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	2200000	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
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	16400000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	34300000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	10500000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	418300000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	451900000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	401400000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	168100000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	88900000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Tax OtherComprehensiveIncomeLossTax	25700000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	9000000.0	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	36900000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Deferred Expense Capitalized Software DeferredTaxLiabilitiesDeferredExpenseCapitalizedSoftware	268100000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Deferred Expense Capitalized Software DeferredTaxLiabilitiesDeferredExpenseCapitalizedSoftware	249400000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	99700000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	99800000	USD
CY2020Q4	ntrs	Deferred Tax Liabilities Compensation And Benefits DeferredTaxLiabilitiesCompensationAndBenefits	31000000.0	USD
CY2019Q4	ntrs	Deferred Tax Liabilities Compensation And Benefits DeferredTaxLiabilitiesCompensationAndBenefits	8300000	USD
CY2020Q4	ntrs	Deferred Tax Liabilities State Taxes DeferredTaxLiabilitiesStateTaxes	67400000	USD
CY2019Q4	ntrs	Deferred Tax Liabilities State Taxes DeferredTaxLiabilitiesStateTaxes	66400000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	372600000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	206700000	USD
CY2020Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	847800000	USD
CY2019Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	667500000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Provision For Loan Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses	54500000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Provision For Loan Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses	26100000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	139800000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	147000000.0	USD
CY2020Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	194300000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	173100000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	143300000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	55200000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	29800000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	139100000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	708700000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	524200000	USD
CY2020	ntrs	Amortization Period For Prior Service Cost Remaining AmortizationPeriodForPriorServiceCostRemaining	P1Y
CY2020	us-gaap	Defined Benefit Plan Actuarial Gain Loss DefinedBenefitPlanActuarialGainLoss	-176000000.0	USD
CY2019	us-gaap	Defined Benefit Plan Actuarial Gain Loss DefinedBenefitPlanActuarialGainLoss	-256200000	USD
CY2020	ntrs	Number Of Investments Held In Diversified Portfolios NumberOfInvestmentsHeldInDiversifiedPortfolios	1	investment
CY2019Q4	us-gaap	Derivative Number Of Instruments Held DerivativeNumberOfInstrumentsHeld	5	numberOfDerivativeInstruments
CY2020Q4	us-gaap	Derivative Number Of Instruments Held DerivativeNumberOfInstrumentsHeld	5	numberOfDerivativeInstruments
CY2020	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets	0.0525
CY2020	ntrs	Defined Benefit Plan Minimum Retirement Age DefinedBenefitPlanMinimumRetirementAge	55	age
CY2020	ntrs	Defined Benefit Plan Minimum Service Term DefinedBenefitPlanMinimumServiceTerm	P15Y
CY2020	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	62900000	USD
CY2019	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	57600000	USD
CY2018	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	54400000	USD
CY2020	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	91400000	USD
CY2019	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	107900000	USD
CY2018	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	130900000	USD
CY2020	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	22900000	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
CY2020Q4	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	70800000	USD
CY2020	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1	P2Y
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested In Period Fair Value1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1	4500000	USD
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
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	13600000	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
CY2020	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	19500000	USD
CY2019	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	44000000.0	USD
CY2018	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	32600000	USD
CY2020	ntrs	Employee Service Share Based Compensation Tax Benefit Realized From Exercise Of Stock Option EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOption	13400000	USD
CY2019	ntrs	Employee Service Share Based Compensation Tax Benefit Realized From Exercise Of Stock Option EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOption	35200000	USD
CY2018	ntrs	Employee Service Share Based Compensation Tax Benefit Realized From Exercise Of Stock Option EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOption	27700000	USD
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
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod	0	shares
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	0
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested Number Of Shares SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares	270110	shares
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested Weighted Average Grant Date Fair Value SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue	16.71
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Nonvested Options Forfeited Number Of Shares SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedNumberOfShares	0	shares
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Nonvested Options Forfeited Weighted Average Grant Date Fair Value SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedWeightedAverageGrantDateFairValue	0
CY2020Q4	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Nonvested Number Of Shares SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares	114829	shares
CY2020Q4	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Nonvested Weighted Average Grant Date Fair Value SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue	19.18
CY2020Q4	us-gaap	Deferred Compensation Arrangement With Individual Cash Award Granted Amount DeferredCompensationArrangementWithIndividualCashAwardGrantedAmount	296200000	USD
	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	2321400000	USD
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
CY2020	us-gaap	Loss Contingency Disclosures LossContingencyDisclosures	Commitments and Contingent Liabilities<div style="margin-bottom:9pt;margin-top:9pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:120%">Off-Balance Sheet Financial Instruments, Guarantees and Other Commitments. </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Northern Trust, in the normal course of business, enters into various types of commitments and issues letters of credit to meet the liquidity and credit enhancement needs of its clients. The contractual amounts of these instruments represent the potential credit exposure should the instrument be fully drawn upon and the client default. To control the credit risk associated with entering into commitments and issuing letters of credit, Northern Trust subjects such activities to the same credit quality and monitoring controls as its lending activities. </span></div><div style="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The following table provides details of Northern Trust's off-balance sheet financial instruments as of December 31, 2020 and 2019.</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:120%">TABLE 128: SUMMARY OF OFF-BALANCE SHEET FINANCIAL INSTRUMENTS</span></div><div style="margin-bottom:5pt;margin-top:5pt"><table style="border-collapse:collapse;display:inline-table;vertical-align:top;width:100.000%"><tr><td style="width:1.0%"/><td style="width:35.263%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:9.506%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:9.506%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:9.506%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:9.506%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:9.506%"/><td style="width:0.1%"/><td style="width:1.0%"/><td style="width:9.507%"/><td style="width:0.1%"/></tr><tr><td colspan="3" style="padding:0 1pt"/><td colspan="18" style="padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:7pt;font-weight:400;line-height:100%">DECEMBER 31,</span></td></tr><tr><td colspan="3" style="padding:0 1pt"/><td colspan="9" style="padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:7pt;font-weight:700;line-height:100%">2020</span></td><td colspan="9" style="padding:2px 1pt;text-align:center;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:7pt;font-weight:400;line-height:100%">2019</span></td></tr><tr><td colspan="3" style="padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:7pt;font-weight:400;line-height:100%">($ In Millions)</span></td><td colspan="3" style="border-top:1pt solid #000;padding:2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:7pt;font-weight:700;line-height:100%">ONE YEAR AND LESS</span></td><td colspan="3" style="border-top:1pt solid #000;padding:2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:7pt;font-weight:700;line-height:100%">OVER ONE YEAR</span></td><td colspan="3" style="border-top:1pt solid #000;padding:2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:7pt;font-weight:700;line-height:100%">TOTAL</span></td><td colspan="3" style="border-top:1pt solid #000;padding:2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:7pt;font-weight:400;line-height:100%">ONE YEAR AND LESS</span></td><td colspan="3" style="border-top:1pt solid #000;padding:2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:7pt;font-weight:400;line-height:100%">OVER ONE YEAR</span></td><td colspan="3" style="border-top:1pt solid #000;padding:2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:7pt;font-weight:400;line-height:100%">TOTAL</span></td></tr><tr><td colspan="3" style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 1pt;text-align:left;vertical-align:bottom"><div><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Undrawn Commitments to Extend Credit</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:5.2pt;font-weight:400;line-height:100%;position:relative;top:-2.8pt;vertical-align:baseline">(1)</span></div></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">11,260.5</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">17,678.0</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">28,938.5</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">7,500.2 </span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">16,906.0 </span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">24,406.2 </span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#ffffff;padding:2px 1pt;text-align:left;vertical-align:bottom"><div><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Standby Letters of Credit and Financial Guarantees</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:5.2pt;font-weight:400;line-height:100%;position:relative;top:-2.8pt;vertical-align:baseline">(2)</span></div></td><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">1,228.1</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">763.5</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">1,991.6</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">1,567.6 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">845.9 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">2,413.5 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#cceeff;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Commercial Letters of Credit</span></td><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">54.6</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">—</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">54.6</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">32.3 </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">— </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="2" style="background-color:#cceeff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">32.3 </span></td><td style="background-color:#cceeff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#ffffff;padding:2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Custody Securities Lent with Indemnification</span></td><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">157,478.0</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">—</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">157,478.0</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">138,085.9 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">— </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td colspan="2" style="background-color:#ffffff;padding:2px 0 2px 1pt;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">138,085.9 </span></td><td style="background-color:#ffffff;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr><tr><td colspan="3" style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 1pt;text-align:left;vertical-align:top"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">Total Off-Balance Sheet Financial Instruments</span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">170,021.2</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">18,441.5</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:100%">188,462.7</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%"> </span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">147,186.0 </span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">17,751.9 </span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0 2px 1pt;text-align:left;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">$</span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 0;text-align:right;vertical-align:bottom"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:400;line-height:100%">164,937.9 </span></td><td style="background-color:#cceeff;border-top:1pt solid #000;padding:2px 1pt 2px 0;text-align:right;vertical-align:bottom"/></tr></table></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:4.55pt;font-style:italic;font-weight:400;line-height:120%;position:relative;top:-2.44pt;vertical-align:baseline">(1)</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:7pt;font-style:italic;font-weight:400;line-height:120%"> These amounts exclude $384.7 million and $243.6 million of commitments participated to others at December 31, 2020 and 2019, respectively.</span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:4.55pt;font-style:italic;font-weight:400;line-height:120%;position:relative;top:-2.44pt;vertical-align:baseline">(2)</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:7pt;font-style:italic;font-weight:400;line-height:120%"> These amounts include $24.2 million and $44.5 million of standby letters of credit secured by cash deposits or participated to others as of December 31, 2020 and 2019, respectively.</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:700;line-height:120%">Undrawn Commitments to Extend Credit</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> generally have fixed expiration dates or other termination clauses. Since a significant portion of the commitments are expected to expire without being drawn upon, the total commitment amount does not necessarily represent future loans or liquidity requirements.</span></div><div style="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:700;line-height:120%">Standby Letters of Credit</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> obligate Northern Trust to meet certain financial obligations of its clients, if, under the contractual terms of the agreement, the clients are unable to do so. These instruments are primarily issued to support public and private financial commitments, including commercial paper, bond financing, initial margin requirements on futures exchanges, and similar transactions. Northern Trust is obligated to meet the entire financial obligation of these agreements and in certain cases is able to recover the amounts paid through recourse against collateral received or other participants.</span></div><div style="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:700;line-height:120%">Financial Guarantees</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> are issued by Northern Trust to guarantee the performance of a client to a third party under certain arrangements.</span></div><div style="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:700;line-height:120%">Commercial Letters of Credit</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> are instruments issued by Northern Trust on behalf of its clients that authorize a third party (the beneficiary) to draw drafts up to a stipulated amount under the specified terms and conditions of the agreement and other similar instruments. Commercial letters of credit are issued primarily to facilitate international trade.</span></div><div style="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:700;line-height:120%">Custody Securities Lent with Indemnification</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> involves Northern Trust lending securities owned by clients to borrowers who are reviewed and approved by the Northern Trust Capital Markets Credit Committee, as part of its securities custody activities and at the direction of its clients. In connection with these activities, Northern Trust has issued indemnifications to certain clients against certain losses that are a direct result of a borrower’s failure to return securities when due, should the value of such securities exceed the value of the collateral required to be posted. Borrowers are required to collateralize fully securities received with cash or marketable securities. As securities are loaned, collateral is maintained at a minimum 100% of the fair value of the securities plus accrued interest. The collateral is revalued on a daily basis. The amount of securities loaned as of December 31, 2020 and 2019 subject to indemnification was $157.5 billion and $138.1 billion, respectively. Because of the credit quality of the borrowers and the requirement to fully collateralize securities borrowed, management believes that the exposure to credit loss from this activity is not significant and no liability was recorded at December 31, 2020, or 2019 related to these indemnifications.</span></div><div style="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:120%">Legal Proceedings.</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> 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="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">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="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">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="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">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="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">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. No material accruals have been recorded for pending litigation or threatened legal actions or regulatory matters. </span></div><div style="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">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 December 31, 2020, the Corporation has estimated the range of reasonably possible loss for these matters to be from zero to approximately $20 million 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="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">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="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:115%">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 two 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. In January 2021, the Cour de Cassation, the highest court in France, reversed the June 2018 appellate court ruling, requiring a re-trial at the appellate court level. The re-trial proceedings in the appellate court have not yet been scheduled. 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="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:8pt;font-weight:700;line-height:120%"> </span></div><div style="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:120%">Visa Class B Common Shares.</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> 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 $600 million and $300 million, 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="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">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, </span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">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="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">In June 2016 and 2015, Northern Trust recorded a $123.1 million and $99.9 million net gain on the sale of 1.1 million and 1.0 million 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 4.1 million Visa Class B common shares, which are recorded at their original cost basis of zero, as of both December 31, 2020 and 2019.</span></div><div style="text-align:justify;text-indent:18pt"><span><br/></span></div><div style="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:120%">Clearing and Settlement Organizations.</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> 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="text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">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 December 31, 2020 and 2019, 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>
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CY2020Q4	us-gaap	Derivative Liability Fair Value Gross Asset DerivativeLiabilityFairValueGrossAsset	2817100000	USD
CY2019Q4	us-gaap	Derivative Asset Fair Value Gross Liability DerivativeAssetFairValueGrossLiability	2338000000.0	USD
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CY2020Q4	us-gaap	Derivative Assets DerivativeAssets	1050400000	USD
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CY2019Q4	us-gaap	Derivative Assets DerivativeAssets	1049700000	USD
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CY2019Q4	us-gaap	Hedged Asset Fair Value Hedge HedgedAssetFairValueHedge	2981000000.0	USD
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CY2019Q4	ntrs	Other Liabilities Excluding Derivatives And Non Financial Instruments OtherLiabilitiesExcludingDerivativesAndNonFinancialInstruments	3100000000	USD
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CY2019Q4	us-gaap	Derivative Net Liability Position Aggregate Fair Value DerivativeNetLiabilityPositionAggregateFairValue	766200000	USD
CY2020Q4	us-gaap	Collateral Already Posted Aggregate Fair Value CollateralAlreadyPostedAggregateFairValue	1044000000.0	USD
CY2019Q4	us-gaap	Collateral Already Posted Aggregate Fair Value CollateralAlreadyPostedAggregateFairValue	327100000	USD
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CY2019Q4	us-gaap	Collateral Securities Repledged Delivered Or Used CollateralSecuritiesRepledgedDeliveredOrUsed	0	USD
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CY2018	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	307200000	USD
CY2020	us-gaap	Noninterest Income Other NoninterestIncomeOther	372200000	USD
CY2019	us-gaap	Noninterest Income Other NoninterestIncomeOther	292200000	USD
CY2018	us-gaap	Noninterest Income Other NoninterestIncomeOther	276600000	USD
CY2020	us-gaap	Noninterest Income NoninterestIncome	4657600000	USD
CY2019	us-gaap	Noninterest Income NoninterestIncome	4395200000	USD
CY2018	us-gaap	Noninterest Income NoninterestIncome	4337500000	USD
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CY2020	ntrs	Revenue Including Fully Taxable Equivalent Adjustment RevenueIncludingFullyTaxableEquivalentAdjustment	6135200000	USD
CY2019	ntrs	Revenue Including Fully Taxable Equivalent Adjustment RevenueIncludingFullyTaxableEquivalentAdjustment	6105900000	USD
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CY2020	us-gaap	Noninterest Expense NoninterestExpense	4348200000	USD
CY2019	us-gaap	Noninterest Expense NoninterestExpense	4143500000	USD
CY2018	us-gaap	Noninterest Expense NoninterestExpense	4016900000	USD
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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
CY2020	ntrs	Income Tax Expense Benefit Including Fully Taxable Equivalent Adjustment IncomeTaxExpenseBenefitIncludingFullyTaxableEquivalentAdjustment	452700000	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
CY2020	us-gaap	Net Income Loss NetIncomeLoss	1209300000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	1492200000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	1556400000	USD
CY2020	ntrs	Segment Reporting Information Consolidated Average Assets SegmentReportingInformationConsolidatedAverageAssets	136811100000	USD
CY2019	ntrs	Segment Reporting Information Consolidated Average Assets SegmentReportingInformationConsolidatedAverageAssets	117551400000	USD
CY2018	ntrs	Segment Reporting Information Consolidated Average Assets SegmentReportingInformationConsolidatedAverageAssets	122946600000	USD
CY2020	ntrs	Segment Reporting Information Fully Taxable Equivalent Adjustment SegmentReportingInformationFullyTaxableEquivalentAdjustment	34400000	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
CY2020Q4	us-gaap	Assets Assets	170003900000	USD
CY2020	us-gaap	Revenues Revenues	6100800000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	1627600000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	1209300000	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
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

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$NTRS
NORTHERN TRUST CORP Stock $ntrs

2019 Q4 Form 10-K Financial Statement

#000007312421000071 Filed on February 23, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$NTRS NORTHERN TRUST CORP Stock $ntrs

2019 Q4 Form 10-K Financial Statement

#000007312421000071 Filed on February 23, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$NTRS
NORTHERN TRUST CORP Stock $ntrs