$AJG
Arthur J. Gallagher & Co. Stock $ajg

$ajg Overview Financials Valuation SEC Filings Company Website

2020 Q4 Form 10-K Financial Statement

#000156459021004555 Filed on February 08, 2021

Income Statement

Concept	2020 Q4	2020	2019 Q4
Revenue	$1.704B	$7.004B	$1.721B
YoY Change	-1.03%	-2.66%	3.86%
Cost Of Revenue	$1.123B	$882.1M	$1.176B
YoY Change	-4.51%	-34.79%	-4.26%
Gross Profit	$580.6M	$6.122B	$545.3M
YoY Change	6.47%	4.78%	27.11%
Gross Profit Margin	34.08%	87.41%	31.68%
Selling, General & Admin		$126.5M
YoY Change
% of Gross Profit		2.07%
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$133.5M	$145.1M	$129.6M
YoY Change	3.01%	3.35%	18.03%
% of Gross Profit	22.99%	2.37%	23.77%
Operating Expenses	$379.2M	$906.5M	$413.2M
YoY Change	-8.23%	-15.16%	18.29%
Operating Profit	$201.4M	$5.215B	$132.1M
YoY Change	52.46%	9.24%	65.75%
Interest Expense	-$43.40M	$196.4M	-$48.10M
YoY Change	-9.77%	9.23%	31.78%
% of Operating Profit	-21.55%	3.77%	-36.41%
Other Income/Expense, Net
YoY Change
Pretax Income	$133.7M	$870.9M	$84.00M
YoY Change	59.17%	39.1%	94.44%
Income Tax	-$19.40M	$12.80M	$11.50M
% Of Pretax Income	-14.51%	1.47%	13.69%
Net Earnings	$142.2M	$818.8M	$98.50M
YoY Change	44.37%	22.43%	-16.03%
Net Earnings / Revenue	8.35%	11.69%	5.72%
Basic Earnings Per Share	$0.74	$4.29	$0.53
Diluted Earnings Per Share	$0.72	$4.20	$0.51
COMMON SHARES
Basic Shares Outstanding		191.0M
Diluted Shares Outstanding

Balance Sheet

Concept	2020 Q4	2020	2019 Q4
SHORT-TERM ASSETS
Cash & Short-Term Investments	$665.0M	$665.0M	$605.0M
YoY Change	9.92%	9.92%	-0.33%
Cash & Equivalents	$664.6M	$665.0M	$604.8M
Short-Term Investments
Other Short-Term Assets	$1.114B	$3.124B	$1.074B
YoY Change	3.68%	39.9%	4.88%
Inventory
Prepaid Expenses	$112.1M		$115.5M
Receivables		$603.0M
Other Receivables		$6.733B
Total Short-Term Assets	$11.12B	$11.12B	$9.118B
YoY Change	22.01%	22.0%	12.3%
LONG-TERM ASSETS
Property, Plant & Equipment	$450.7M	$825.0M	$467.4M
YoY Change	-3.57%	-4.18%	6.98%
Goodwill	$6.127B		$5.619B
YoY Change	9.05%		21.47%
Intangibles	$2.400B		$2.319B
YoY Change	3.5%		30.78%
Long-Term Investments	$22.40M	$22.00M	$40.00M
YoY Change	-44.0%
Other Assets	$769.9M	$1.833B	$773.6M
YoY Change	-0.48%	6.63%	34.87%
Total Long-Term Assets	$11.21B	$11.21B	$10.52B
YoY Change	6.56%	6.56%	28.02%
TOTAL ASSETS
Total Short-Term Assets	$11.12B	$11.12B	$9.118B
Total Long-Term Assets	$11.21B	$11.21B	$10.52B
Total Assets	$22.33B	$22.33B	$19.63B
YoY Change	13.73%	13.73%	20.21%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$7.785B	$7.785B	$6.349B
YoY Change	22.62%	22.62%	10.61%
Accrued Expenses	$1.596B	$1.596B	$1.321B
YoY Change	20.82%	20.82%	27.39%
Deferred Revenue
YoY Change
Short-Term Debt	$75.00M	$204.0M	$620.0M
YoY Change	-87.9%	19.3%	69.86%
Long-Term Debt Due	$75.00M	$75.00M	$620.0M
YoY Change	-87.9%	-87.9%	69.86%
Total Short-Term Liabilities	$10.14B	$10.14B	$8.921B
YoY Change	13.61%	13.61%	15.95%
LONG-TERM LIABILITIES
Long-Term Debt	$4.266B	$4.266B	$3.816B
YoY Change	11.79%	11.79%	23.44%
Other Long-Term Liabilities	$1.311B	$1.698B	$1.272B
YoY Change	3.11%	0.95%	41.15%
Total Long-Term Liabilities	$5.577B	$5.964B	$5.088B
YoY Change	9.62%	8.48%	27.44%
TOTAL LIABILITIES
Total Short-Term Liabilities	$10.14B	$10.14B	$8.921B
Total Long-Term Liabilities	$5.577B	$5.964B	$5.088B
Total Liabilities	$16.10B	$16.15B	$14.42B
YoY Change	11.65%	11.51%	22.57%
SHAREHOLDERS EQUITY
Retained Earnings	$2.372B		$1.901B
YoY Change	24.74%		21.99%
Common Stock	$4.458B		$4.014B
YoY Change	11.07%		7.73%
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$6.186B	$6.186B	$5.156B
YoY Change
Total Liabilities & Shareholders Equity	$22.33B	$22.33B	$19.63B
YoY Change	13.73%	13.73%	20.21%

Cashflow Statement

Concept	2020 Q4	2020	2019 Q4
OPERATING ACTIVITIES
Net Income	$142.2M	$818.8M	$98.50M
YoY Change	44.37%	22.43%	-16.03%
Depreciation, Depletion And Amortization	$133.5M	$145.1M	$129.6M
YoY Change	3.01%	3.35%	18.03%
Cash From Operating Activities	$364.9M	$1.807B	$350.1M
YoY Change	4.23%	51.72%	34.4%
INVESTING ACTIVITIES
Capital Expenditures	-$19.80M	-$99.30M	-$31.10M
YoY Change	-36.33%	-28.46%	-7.44%
Acquisitions
YoY Change
Other Investing Activities	-$234.2M	-$317.5M	-$365.1M
YoY Change	-35.85%	-74.35%	63.8%
Cash From Investing Activities	-$254.0M	-$416.8M	-$396.2M
YoY Change	-35.89%	-71.23%	54.46%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net		$111.9M
YoY Change		10.57%
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-123.9M	-505.1M	9.700M
YoY Change	-1377.32%	-179.12%	86.54%
NET CHANGE
Cash From Operating Activities	364.9M	1.807B	350.1M
Cash From Investing Activities	-254.0M	-416.8M	-396.2M
Cash From Financing Activities	-123.9M	-505.1M	9.700M
Net Change In Cash	-13.00M	950.4M	-36.40M
YoY Change	-64.29%	145.52%	-495.65%
FREE CASH FLOW
Cash From Operating Activities	$364.9M	$1.807B	$350.1M
Capital Expenditures	-$19.80M	-$99.30M	-$31.10M
Free Cash Flow	$384.7M	$1.906B	$381.2M
YoY Change	0.92%	43.35%	29.62%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value
CY2020	dei	Amendment Flag AmendmentFlag	false
CY2020	us-gaap	Open Tax Year OpenTaxYear	2011 2012
CY2020	ajg	Expected Period Of Return On Plan Assets ExpectedPeriodOfReturnOnPlanAssets	P10Y
CY2019	ajg	Expected Period Of Return On Plan Assets ExpectedPeriodOfReturnOnPlanAssets	P10Y
CY2020Q4	us-gaap	Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1	P1Y
CY2020Q4	us-gaap	Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1	P1Y
CY2020Q4	us-gaap	Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1	P1Y
CY2020	dei	Entity Address City Or Town EntityAddressCityOrTown	Rolling Meadows
CY2020	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
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	Document Transition Report DocumentTransitionReport	false
CY2020	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	36-2151613
CY2020	dei	Entity Address Address Line1 EntityAddressAddressLine1	2850 Golf Road
CY2020	dei	Entity Address State Or Province EntityAddressStateOrProvince	IL
CY2020	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	60008-4050
CY2020	dei	City Area Code CityAreaCode	630
CY2020	dei	Local Phone Number LocalPhoneNumber	773-3800
CY2020	dei	Security12b Title Security12bTitle	Common Stock, par value $1.00 per share
CY2020Q4	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	1085800000
CY2020	dei	Trading Symbol TradingSymbol	AJG
CY2020	dei	Security Exchange Name SecurityExchangeName	NYSE
CY2020	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	Yes
CY2020	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2020	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2020	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2020	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
CY2020	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
CY2020	dei	Icfr Auditor Attestation Flag IcfrAuditorAttestationFlag	true
CY2020	dei	Entity Shell Company EntityShellCompany	false
CY2020Q2	dei	Entity Public Float EntityPublicFloat	16249616000
CY2021Q1	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	193740000
CY2018	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	400000000.0
CY2018	ajg	Payments For Proceeds From Settlements Of Terminated Interest Rate Swaps PaymentsForProceedsFromSettlementsOfTerminatedInterestRateSwaps	-2900000
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	638400000
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	162000000.0
CY2020	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	119800000
CY2019	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	6100000
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	950400000
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	2623900000
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	2236800000
CY2018	ajg	Change In Estimated Acquisition Earnout Payables ChangeInEstimatedAcquisitionEarnoutPayables	9600000
CY2020Q4	us-gaap	Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1	P1Y
CY2020Q4	us-gaap	Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1	P1Y
CY2020Q4	us-gaap	Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Expected Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1	P5Y4M24D
CY2019	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Expected Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1	P5Y6M
CY2018	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Expected Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1	P5Y6M
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P3Y10M9D
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1	P1Y9M29D
CY2020	ajg	Sharebased Compensation Arrangement By Sharebased Payment Award Options Nonvested And Expected To Vest Outstanding Weighted Average Remaining Contractual Term SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm	P4Y6M3D
CY2019	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P3Y9M
CY2019	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1	P1Y9M25D
CY2019	ajg	Sharebased Compensation Arrangement By Sharebased Payment Award Options Nonvested And Expected To Vest Outstanding Weighted Average Remaining Contractual Term SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm	P4Y4M9D
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P3Y10M9D
CY2020Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P5Y3M18D
CY2020Q4	us-gaap	Operating Lease Liability Current Statement Of Financial Position Extensible List OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList	ajg:AccruedCompensationAndOtherAccruedLiabilities
CY2020	dei	Entity File Number EntityFileNumber	1-09761
CY2020	dei	Entity Registrant Name EntityRegistrantName	ARTHUR J. GALLAGHER & CO.
CY2020	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	DE
CY2020	dei	Entity Small Business EntitySmallBusiness	false
CY2020	ajg	Revenue From Contract With Customer Before Reimbursements Excluding Assessed Tax RevenueFromContractWithCustomerBeforeReimbursementsExcludingAssessedTax	6851900000
CY2019	ajg	Revenue From Contract With Customer Before Reimbursements Excluding Assessed Tax RevenueFromContractWithCustomerBeforeReimbursementsExcludingAssessedTax	7056400000
CY2018	ajg	Revenue From Contract With Customer Before Reimbursements Excluding Assessed Tax RevenueFromContractWithCustomerBeforeReimbursementsExcludingAssessedTax	6792400000
CY2020	ajg	Revenue From Contract With Customer Excluding Assessed Tax Reimbursements RevenueFromContractWithCustomerExcludingAssessedTaxReimbursements	151700000
CY2019	ajg	Revenue From Contract With Customer Excluding Assessed Tax Reimbursements RevenueFromContractWithCustomerExcludingAssessedTaxReimbursements	138600000
CY2018	ajg	Revenue From Contract With Customer Excluding Assessed Tax Reimbursements RevenueFromContractWithCustomerExcludingAssessedTaxReimbursements	141600000
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	7003600000
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	7195000000.0
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	6934000000.0
CY2020	us-gaap	Labor And Related Expense LaborAndRelatedExpense	3466500000
CY2019	us-gaap	Labor And Related Expense LaborAndRelatedExpense	3339500000
CY2018	us-gaap	Labor And Related Expense LaborAndRelatedExpense	3026300000
CY2020	us-gaap	Operating Expenses OperatingExpenses	906500000
CY2019	us-gaap	Operating Expenses OperatingExpenses	1068500000
CY2018	us-gaap	Operating Expenses OperatingExpenses	903700000
CY2020	ajg	Cost Reimbursements CostReimbursements	151700000
CY2019	ajg	Cost Reimbursements CostReimbursements	138600000
CY2018	ajg	Cost Reimbursements CostReimbursements	141600000
CY2020	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	882100000
CY2019	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	1352800000
CY2018	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	1816000000.0
CY2020	us-gaap	Interest Expense InterestExpense	196400000
CY2019	us-gaap	Interest Expense InterestExpense	179800000
CY2018	us-gaap	Interest Expense InterestExpense	138400000
CY2020	us-gaap	Depreciation Depreciation	145100000
CY2019	us-gaap	Depreciation Depreciation	140400000
CY2018	us-gaap	Depreciation Depreciation	127800000
CY2020	us-gaap	Adjustment For Amortization AdjustmentForAmortization	417300000
CY2019	us-gaap	Adjustment For Amortization AdjustmentForAmortization	334000000.0
CY2018	us-gaap	Adjustment For Amortization AdjustmentForAmortization	291200000
CY2020	ajg	Change In Estimated Acquisition Earnout Payables ChangeInEstimatedAcquisitionEarnoutPayables	-32900000
CY2019	ajg	Change In Estimated Acquisition Earnout Payables ChangeInEstimatedAcquisitionEarnoutPayables	15300000
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	450700000
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	467400000
CY2020	us-gaap	Costs And Expenses CostsAndExpenses	6132700000
CY2019	us-gaap	Costs And Expenses CostsAndExpenses	6568900000
CY2018	us-gaap	Costs And Expenses CostsAndExpenses	6454600000
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	870900000
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	626100000
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	479400000
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	12800000
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-89700000
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-196500000
CY2020	us-gaap	Profit Loss ProfitLoss	858100000
CY2019	us-gaap	Profit Loss ProfitLoss	715800000
CY2018	us-gaap	Profit Loss ProfitLoss	675900000
CY2020	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	39300000
CY2019	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	47000000.0
CY2018	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	42400000
CY2020	us-gaap	Net Income Loss NetIncomeLoss	818800000
CY2019	us-gaap	Net Income Loss NetIncomeLoss	668800000
CY2018	us-gaap	Net Income Loss NetIncomeLoss	633500000
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.29
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.60
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.47
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.20
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.52
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.40
CY2020	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.80
CY2019	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.72
CY2018	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	1.64
CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-400000
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-4700000
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	10300000
CY2020	us-gaap	Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax	183700000
CY2019	us-gaap	Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax	44000000.0
CY2018	us-gaap	Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Arising During Period Net Of Tax OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax	-197700000
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax Parent OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent	-68100000
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax Parent OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent	-22700000
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax Parent OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent	-15600000
CY2020	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	974100000
CY2019	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	741800000
CY2018	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	452300000
CY2020	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	39700000
CY2019	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	47300000
CY2018	us-gaap	Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest	40400000
CY2020	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	934400000
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	694500000
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	411900000
CY2020Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	664600000
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	604800000
CY2020Q4	us-gaap	Restricted Cash Current RestrictedCashCurrent	2909700000
CY2019Q4	us-gaap	Restricted Cash Current RestrictedCashCurrent	2019100000
CY2020Q4	us-gaap	Premiums And Other Receivables Net PremiumsAndOtherReceivablesNet	6436000000.0
CY2019Q4	us-gaap	Premiums And Other Receivables Net PremiumsAndOtherReceivablesNet	5419200000
CY2020Q4	us-gaap	Other Assets Current OtherAssetsCurrent	1113900000
CY2019Q4	us-gaap	Other Assets Current OtherAssetsCurrent	1074400000
CY2020Q4	us-gaap	Assets Current AssetsCurrent	11124200000
CY2019Q4	us-gaap	Assets Current AssetsCurrent	9117500000
CY2019Q4	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	945600000
CY2020Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	769900000
CY2019Q4	us-gaap	Other Assets Noncurrent OtherAssetsNoncurrent	773600000
CY2020Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	373900000
CY2019Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	393500000
CY2020Q4	us-gaap	Goodwill Goodwill	6127000000.0
CY2019Q4	us-gaap	Goodwill Goodwill	5618500000
CY2020Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	2399900000
CY2019Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	2318700000
CY2020Q4	us-gaap	Assets Assets	22331400000
CY2019Q4	us-gaap	Assets Assets	19634800000
CY2020Q4	ajg	Premiums Payable To Underwriting Enterprises PremiumsPayableToUnderwritingEnterprises	7784600000
CY2019Q4	ajg	Premiums Payable To Underwriting Enterprises PremiumsPayableToUnderwritingEnterprises	6348500000
CY2020Q4	ajg	Accrued Compensation And Other Accrued Liabilities AccruedCompensationAndOtherAccruedLiabilities	1596200000
CY2019Q4	ajg	Accrued Compensation And Other Accrued Liabilities AccruedCompensationAndOtherAccruedLiabilities	1347800000
CY2020Q4	us-gaap	Deferred Revenue Current DeferredRevenueCurrent	475600000
CY2019Q4	us-gaap	Deferred Revenue Current DeferredRevenueCurrent	434100000
CY2020Q4	ajg	Premium Financing Borrowings PremiumFinancingBorrowings	203600000
CY2019Q4	ajg	Premium Financing Borrowings PremiumFinancingBorrowings	170600000
CY2020Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	75000000.0
CY2019Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	620000000.0
CY2020Q4	us-gaap	Liabilities Current LiabilitiesCurrent	10135000000.0
CY2019Q4	us-gaap	Liabilities Current LiabilitiesCurrent	8921000000.0
CY2020Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	4266000000.0
CY2019Q4	us-gaap	Long Term Debt Noncurrent LongTermDebtNoncurrent	3816100000
CY2020Q4	us-gaap	Deferred Revenue Noncurrent DeferredRevenueNoncurrent	65700000
CY2019Q4	us-gaap	Deferred Revenue Noncurrent DeferredRevenueNoncurrent	69700000
CY2020Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	320900000
CY2019Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	340900000
CY2020Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	1311100000
CY2019Q4	us-gaap	Other Liabilities Noncurrent OtherLiabilitiesNoncurrent	1271600000
CY2020Q4	us-gaap	Liabilities Liabilities	16098700000
CY2019Q4	us-gaap	Liabilities Liabilities	14419300000
CY2020Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	400000000.0
CY2019Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	400000000.0
CY2020Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	193700000
CY2020Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	193700000
CY2019Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	188100000
CY2019Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	188100000
CY2020Q4	us-gaap	Common Stock Value CommonStockValue	193700000
CY2019Q4	us-gaap	Common Stock Value CommonStockValue	188100000
CY2020Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	4264400000
CY2019Q4	us-gaap	Additional Paid In Capital Common Stock AdditionalPaidInCapitalCommonStock	3825700000
CY2020Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	2371700000
CY2019Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	1901300000
CY2020Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-643600000
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-759600000
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	6186200000
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	5155500000
CY2020Q4	us-gaap	Minority Interest MinorityInterest	46500000
CY2019Q4	us-gaap	Minority Interest MinorityInterest	60000000.0
CY2020Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	6232700000
CY2019Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	5215500000
CY2020Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	22331400000
CY2019Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	19634800000
CY2020	us-gaap	Profit Loss ProfitLoss	858100000
CY2019	us-gaap	Profit Loss ProfitLoss	715800000
CY2018	us-gaap	Profit Loss ProfitLoss	675900000
CY2020	us-gaap	Gain Loss On Investments GainLossOnInvestments	-6300000
CY2019	us-gaap	Gain Loss On Investments GainLossOnInvestments	72000000.0
CY2018	us-gaap	Gain Loss On Investments GainLossOnInvestments	8400000
CY2020	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	562400000
CY2019	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	474400000
CY2018	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	419000000.0
CY2020	ajg	Change In Estimated Acquisition Earnout Payables ChangeInEstimatedAcquisitionEarnoutPayables	-32900000
CY2019	ajg	Change In Estimated Acquisition Earnout Payables ChangeInEstimatedAcquisitionEarnoutPayables	15300000
CY2018	ajg	Change In Estimated Acquisition Earnout Payables ChangeInEstimatedAcquisitionEarnoutPayables	9600000
CY2020	ajg	Amortization Of Deferred Compensation And Restricted Stock AmortizationOfDeferredCompensationAndRestrictedStock	60900000
CY2019	ajg	Amortization Of Deferred Compensation And Restricted Stock AmortizationOfDeferredCompensationAndRestrictedStock	47200000
CY2018	ajg	Amortization Of Deferred Compensation And Restricted Stock AmortizationOfDeferredCompensationAndRestrictedStock	41600000
CY2020	us-gaap	Share Based Compensation ShareBasedCompensation	13600000
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	14000000.0
CY2018	us-gaap	Share Based Compensation ShareBasedCompensation	13700000
CY2020	us-gaap	Business Combination Contingent Consideration Arrangements Change In Amount Of Contingent Consideration Liability1 BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1	-14500000
CY2019	us-gaap	Business Combination Contingent Consideration Arrangements Change In Amount Of Contingent Consideration Liability1 BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1	-16600000
CY2018	us-gaap	Business Combination Contingent Consideration Arrangements Change In Amount Of Contingent Consideration Liability1 BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1	-64600000
CY2020	us-gaap	Foreign Currency Transaction Gain Loss Unrealized ForeignCurrencyTransactionGainLossUnrealized	-2900000
CY2019	us-gaap	Foreign Currency Transaction Gain Loss Unrealized ForeignCurrencyTransactionGainLossUnrealized	-6700000
CY2018	us-gaap	Foreign Currency Transaction Gain Loss Unrealized ForeignCurrencyTransactionGainLossUnrealized	2900000
CY2020	ajg	Increase Decrease In Premiums And Fee Receivable IncreaseDecreaseInPremiumsAndFeeReceivable	796500000
CY2019	ajg	Increase Decrease In Premiums And Fee Receivable IncreaseDecreaseInPremiumsAndFeeReceivable	434700000
CY2018	ajg	Increase Decrease In Premiums And Fee Receivable IncreaseDecreaseInPremiumsAndFeeReceivable	783100000
CY2020	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	18500000
CY2019	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	12800000
CY2018	us-gaap	Increase Decrease In Contract With Customer Liability IncreaseDecreaseInContractWithCustomerLiability	18400000
CY2020	us-gaap	Increase Decrease In Reinsurance Payables IncreaseDecreaseInReinsurancePayables	1154200000
CY2019	us-gaap	Increase Decrease In Reinsurance Payables IncreaseDecreaseInReinsurancePayables	461600000
CY2018	us-gaap	Increase Decrease In Reinsurance Payables IncreaseDecreaseInReinsurancePayables	819700000
CY2020	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	77100000
CY2019	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	60500000
CY2018	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	134700000
CY2020	ajg	Net Change In Accrued Compensation And Other Accrued Liabilities NetChangeInAccruedCompensationAndOtherAccruedLiabilities	-91800000
CY2019	ajg	Net Change In Accrued Compensation And Other Accrued Liabilities NetChangeInAccruedCompensationAndOtherAccruedLiabilities	-77000000.0
CY2018	ajg	Net Change In Accrued Compensation And Other Accrued Liabilities NetChangeInAccruedCompensationAndOtherAccruedLiabilities	-44900000
CY2020	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	51800000
CY2019	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	35500000
CY2018	us-gaap	Increase Decrease In Accrued Income Taxes Payable IncreaseDecreaseInAccruedIncomeTaxesPayable	-46000000.0
CY2020	us-gaap	Increase Decrease In Deferred Income Taxes IncreaseDecreaseInDeferredIncomeTaxes	175600000
CY2019	us-gaap	Increase Decrease In Deferred Income Taxes IncreaseDecreaseInDeferredIncomeTaxes	150700000
CY2018	us-gaap	Increase Decrease In Deferred Income Taxes IncreaseDecreaseInDeferredIncomeTaxes	216000000.0
CY2020	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-28600000
CY2019	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	6600000
CY2018	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	22000000.0
CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	1752500000
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	1119200000
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	765100000
CY2020	us-gaap	Payments For Capital Improvements PaymentsForCapitalImprovements	99300000
CY2019	us-gaap	Stock Issued During Period Value Acquisitions StockIssuedDuringPeriodValueAcquisitions	168000000.0
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	-5600000
CY2019	us-gaap	Profit Loss ProfitLoss	715800000
CY2019	ajg	Minority Interest Increase Decrease From Redemptions MinorityInterestIncreaseDecreaseFromRedemptions	-15100000
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	1100000
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-4700000
CY2019	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	44500000
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	-8900000
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax Parent OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent	-22700000
CY2019	us-gaap	Stock Granted During Period Value Sharebased Compensation StockGrantedDuringPeriodValueSharebasedCompensation	14000000.0
CY2019	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	73700000
CY2019	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	27500000
CY2019	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	323900000
CY2019Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	5215500000
CY2019Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	5215500000
CY2020	us-gaap	Profit Loss ProfitLoss	858100000
CY2020	ajg	Minority Interest Increase Decrease From Redemptions MinorityInterestIncreaseDecreaseFromRedemptions	-6400000
CY2020	us-gaap	Minority Interest Decrease From Distributions To Noncontrolling Interest Holders MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	46800000
CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	100000
CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-400000
CY2020	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	184100000
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationTax	-22400000
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax Parent OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent	-68100000
CY2020	us-gaap	Stock Granted During Period Value Sharebased Compensation StockGrantedDuringPeriodValueSharebasedCompensation	13600000
CY2020	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	77700000
CY2020	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	34200000
CY2019	us-gaap	Payments For Capital Improvements PaymentsForCapitalImprovements	138800000
CY2018	us-gaap	Payments For Capital Improvements PaymentsForCapitalImprovements	124400000
CY2020	ajg	Payments To Acquire Businesses Net Of Cash And Restricted Cash Acquired PaymentsToAcquireBusinessesNetOfCashAndRestrictedCashAcquired	324300000
CY2019	ajg	Payments To Acquire Businesses Net Of Cash And Restricted Cash Acquired PaymentsToAcquireBusinessesNetOfCashAndRestrictedCashAcquired	1266800000
CY2018	ajg	Payments To Acquire Businesses Net Of Cash And Restricted Cash Acquired PaymentsToAcquireBusinessesNetOfCashAndRestrictedCashAcquired	784800000
CY2020	ajg	Net Proceeds From Sales Of Operations NetProceedsFromSalesOfOperations	8200000
CY2019	ajg	Net Proceeds From Sales Of Operations NetProceedsFromSalesOfOperations	81000000.0
CY2018	ajg	Net Proceeds From Sales Of Operations NetProceedsFromSalesOfOperations	14500000
CY2020	us-gaap	Payments For Proceeds From Investments PaymentsForProceedsFromInvestments	1400000
CY2019	us-gaap	Payments For Proceeds From Investments PaymentsForProceedsFromInvestments	52000000.0
CY2018	us-gaap	Payments For Proceeds From Investments PaymentsForProceedsFromInvestments	15600000
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-416800000
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1376600000
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-910300000
CY2020	ajg	Earnout Payments For Acquisitions EarnoutPaymentsForAcquisitions	38800000
CY2019	ajg	Earnout Payments For Acquisitions EarnoutPaymentsForAcquisitions	46300000
CY2018	ajg	Earnout Payments For Acquisitions EarnoutPaymentsForAcquisitions	62100000
CY2020	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	111900000
CY2019	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	101200000
CY2018	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	81900000
CY2018	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	11300000
CY2020	us-gaap	Payments To Minority Shareholders PaymentsToMinorityShareholders	84400000
CY2019	us-gaap	Payments To Minority Shareholders PaymentsToMinorityShareholders	75400000
CY2018	us-gaap	Payments To Minority Shareholders PaymentsToMinorityShareholders	54200000
CY2020	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	347400000
CY2019	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	321100000
CY2020	ajg	Net Borrowings On Premium Financing Debt Facility NetBorrowingsOnPremiumFinancingDebtFacility	16000000.0
CY2018	us-gaap	Repayments Of Lines Of Credit RepaymentsOfLinesOfCredit	3000000000.0
CY2019	us-gaap	Proceeds From Issuance Of Long Term Debt ProceedsFromIssuanceOfLongTermDebt	725000000.0
CY2020	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	1300000
CY2019	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	3900000
CY2018	us-gaap	Payments Of Debt Issuance Costs PaymentsOfDebtIssuanceCosts	1300000
CY2020	ajg	Payments For Proceeds From Settlements Of Terminated Interest Rate Swaps PaymentsForProceedsFromSettlementsOfTerminatedInterestRateSwaps	66000000.0
CY2019	ajg	Payments For Proceeds From Settlements Of Terminated Interest Rate Swaps PaymentsForProceedsFromSettlementsOfTerminatedInterestRateSwaps	15300000
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-505100000
CY2018	us-gaap	Effect Of Exchange Rate On Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	-85000000.0
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	387100000
CY2018	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-68200000
CY2017Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	2305000000.0
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	3574300000
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	2623900000
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations	2236800000
CY2017Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	4299700000
CY2018	us-gaap	Profit Loss ProfitLoss	675900000
CY2018	ajg	Minority Interest Increase Decrease From Redemptions MinorityInterestIncreaseDecreaseFromRedemptions	-700000
CY2018	us-gaap	Minority Interest Decrease From Distributions To Noncontrolling Interest Holders MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	38000000.0
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	6200000
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	10300000
CY2018	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax	-199700000
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax Parent OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent	-15600000
CY2018	us-gaap	Stock Granted During Period Value Sharebased Compensation StockGrantedDuringPeriodValueSharebasedCompensation	13700000
CY2018	us-gaap	Stock Issued During Period Value Acquisitions StockIssuedDuringPeriodValueAcquisitions	61600000
CY2018	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	58600000
CY2018	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	23300000
CY2018	ajg	Deferred Compensation And Restricted Stock Expenses Benefit DeferredCompensationAndRestrictedStockExpensesBenefit	15800000
CY2018	us-gaap	Stock Repurchased During Period Value StockRepurchasedDuringPeriodValue	11300000
CY2018	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	303300000
CY2018Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	4569700000
CY2019	us-gaap	Minority Interest Decrease From Distributions To Noncontrolling Interest Holders MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	43000000.0
CY2019	ajg	Deferred Compensation And Restricted Stock Expenses Benefit DeferredCompensationAndRestrictedStockExpensesBenefit	4700000
CY2020	us-gaap	Stock Issued During Period Value Acquisitions StockIssuedDuringPeriodValueAcquisitions	309100000
CY2020	ajg	Deferred Compensation And Restricted Stock Expenses Benefit DeferredCompensationAndRestrictedStockExpensesBenefit	9700000
CY2020	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	348400000
CY2020Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	6232700000
CY2020	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	3
CY2020Q4	ajg	Number Of Commercial Clean Coal Production Facilities NumberOfCommercialCleanCoalProductionFacilities	35
CY2020	ajg	Number Of Countries In Which Company Has Operations NumberOfCountriesInWhichCompanyHasOperations	49
CY2020	ajg	Number Of Countries In Which Company Does Business Through Network Of Correspondent Brokers And Consultants NumberOfCountriesInWhichCompanyDoesBusinessThroughNetworkOfCorrespondentBrokersAndConsultants	150
CY2020Q4	us-gaap	Equity Method Investment Ownership Percentage EquityMethodInvestmentOwnershipPercentage	0.50
CY2020	us-gaap	Variable Interest Entity Ownership Percentage VariableInterestEntityOwnershipPercentage	0.50
CY2020	us-gaap	Use Of Estimates UseOfEstimates	<p style="text-align:left;margin-bottom:0pt;margin-top:18pt;text-indent:0%;font-weight:bold;font-size:10pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">Use of Estimates</p> <p style="text-align:left;margin-bottom:0pt;margin-top:6pt;text-indent:0%;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">The preparation of our consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. These accounting principles require us to make estimates and assumptions that affect the reported amounts of assets and liabilities and revenues and expenses, and the disclosure of contingent assets and liabilities at the date of our consolidated financial statements. We periodically evaluate our estimates and assumptions, including those relating to the valuation of goodwill and other intangible assets, right-of-use assets, investments (including our IRC Section 45 investments), income taxes, revenue recognition, deferred costs, stock-based compensation, claims handling obligations, retirement plans, litigation and contingencies. We base our estimates on historical experience and various assumptions that we believe to be reasonable based on specific circumstances. Such estimates and assumptions could change in the future as more information becomes known, which could impact the amounts reported and disclosed herein.</p>
CY2020	ajg	Description Of Contracts Renewal Period DescriptionOfContractsRenewalPeriod	one year or less
CY2020	ajg	Percentage Of Commissions And Fee Revenues Recognized On Effective Date Of Insurance Contract PercentageOfCommissionsAndFeeRevenuesRecognizedOnEffectiveDateOfInsuranceContract	0.80
CY2020	ajg	Percentage Of Commissions And Fee Revenues Recognized In First Three Months Of Insurance Contract PercentageOfCommissionsAndFeeRevenuesRecognizedInFirstThreeMonthsOfInsuranceContract	0.15
CY2020	ajg	Percentage Of Commissions And Fee Revenues Recognized After First Three Months Of Insurance Contract PercentageOfCommissionsAndFeeRevenuesRecognizedAfterFirstThreeMonthsOfInsuranceContract	0.05
CY2020	ajg	Allowances For Estimated Policy Cancellations AllowancesForEstimatedPolicyCancellations	9900000
CY2019	ajg	Allowances For Estimated Policy Cancellations AllowancesForEstimatedPolicyCancellations	8300000
CY2020Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	10100000
CY2019Q4	us-gaap	Allowance For Doubtful Accounts Receivable AllowanceForDoubtfulAccountsReceivable	8700000
CY2020	ajg	Insurance Contracts Premium Financing Terms InsuranceContractsPremiumFinancingTerms	premium financing contracts are structured to minimize potential bad debt expense to us. Such receivables are generally considered delinquent after seven days of the payment due date. In normal course, insurance policies are cancelled within one month of the contractual payment due date if the payment remains delinquent.
CY2020Q4	us-gaap	Accounts Receivable Billed For Long Term Contracts Or Programs AccountsReceivableBilledForLongTermContractsOrPrograms	442700000
CY2019Q4	us-gaap	Accounts Receivable Billed For Long Term Contracts Or Programs AccountsReceivableBilledForLongTermContractsOrPrograms	388100000
CY2020	us-gaap	Impairment Of Intangible Assets Finitelived ImpairmentOfIntangibleAssetsFinitelived	51700000
CY2019	us-gaap	Impairment Of Intangible Assets Finitelived ImpairmentOfIntangibleAssetsFinitelived	100000
CY2018	us-gaap	Impairment Of Intangible Assets Finitelived ImpairmentOfIntangibleAssetsFinitelived	10600000
CY2019Q1	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	379600000
CY2019Q1	us-gaap	Operating Lease Liability OperatingLeaseLiability	420300000
CY2019Q1	us-gaap	Deferred Rent Receivables Net Noncurrent DeferredRentReceivablesNetNoncurrent	38300000
CY2020	us-gaap	Business Acquisition Equity Interests Issued Or Issuable Number Of Shares Issued BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued	1843000
CY2020	us-gaap	Business Combination Consideration Transferred Equity Interests Issued And Issuable BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable	189700000
CY2020	us-gaap	Payments To Acquire Businesses Gross PaymentsToAcquireBusinessesGross	398300000
CY2020Q4	ajg	Business Combination Recognized Identifiable Assets Acquired And Liabilities Accrued Liability BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAccruedLiability	50000000.0
CY2020Q4	us-gaap	Escrow Deposit EscrowDeposit	30700000
CY2020	ajg	Recorded Earn Out Payable RecordedEarnOutPayable	207400000
CY2020Q4	ajg	Business Acquisition Cost Of Acquired Entity Purchase Price Net BusinessAcquisitionCostOfAcquiredEntityPurchasePriceNet	876100000
CY2020Q4	ajg	Maximum Potential Earnout Payable MaximumPotentialEarnoutPayable	387900000
CY2020	us-gaap	Business Combination Separately Recognized Transactions Additional Disclosures Acquisition Cost Expensed BusinessCombinationSeparatelyRecognizedTransactionsAdditionalDisclosuresAcquisitionCostExpensed	32500000
CY2019	us-gaap	Business Combination Separately Recognized Transactions Additional Disclosures Acquisition Cost Expensed BusinessCombinationSeparatelyRecognizedTransactionsAdditionalDisclosuresAcquisitionCostExpensed	27000000.0
CY2018	us-gaap	Business Combination Separately Recognized Transactions Additional Disclosures Acquisition Cost Expensed BusinessCombinationSeparatelyRecognizedTransactionsAdditionalDisclosuresAcquisitionCostExpensed	18800000
CY2020	us-gaap	Business Acquisitions Pro Forma Net Income Loss BusinessAcquisitionsProFormaNetIncomeLoss	65400000
CY2019	us-gaap	Business Acquisitions Pro Forma Net Income Loss BusinessAcquisitionsProFormaNetIncomeLoss	11700000
CY2018	us-gaap	Business Acquisitions Pro Forma Net Income Loss BusinessAcquisitionsProFormaNetIncomeLoss	9200000
CY2020	us-gaap	Number Of Businesses Acquired NumberOfBusinessesAcquired	135
CY2019	us-gaap	Number Of Businesses Acquired NumberOfBusinessesAcquired	116
CY2018	us-gaap	Number Of Businesses Acquired NumberOfBusinessesAcquired	112
CY2020	ajg	Business Combination Aggregate Earnout Obligation Maximum BusinessCombinationAggregateEarnoutObligationMaximum	1128100000
CY2020	ajg	Business Combination Aggregate Earnout Obligation Recorded Maximum BusinessCombinationAggregateEarnoutObligationRecordedMaximum	592200000
CY2020Q4	ajg	Business Combination Aggregate Earnout Obligation Expected Settlement In Cash Or Stock At Option BusinessCombinationAggregateEarnoutObligationExpectedSettlementInCashOrStockAtOption	493700000
CY2020Q4	ajg	Business Combination Aggregate Earnout Obligation Expected Settlement In Cash BusinessCombinationAggregateEarnoutObligationExpectedSettlementInCash	98500000
CY2019	ajg	Business Combination Aggregate Earnout Obligation Maximum BusinessCombinationAggregateEarnoutObligationMaximum	982900000
CY2019	ajg	Business Combination Aggregate Earnout Obligation Recorded Maximum BusinessCombinationAggregateEarnoutObligationRecordedMaximum	565000000.0
CY2020Q4	ajg	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Cash And Equivalents And Restricted Cash BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalentsAndRestrictedCash	34000000.0
CY2020Q4	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Current Assets Other BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther	88000000.0
CY2020Q4	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Property Plant And Equipment BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment	3200000
CY2020Q4	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Noncurrent Assets BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentAssets	27600000
CY2020Q4	ajg	Business Acquisitions Purchase Price Allocation Goodwill Amount BusinessAcquisitionsPurchasePriceAllocationGoodwillAmount	359600000
CY2020Q4	ajg	Expiration Lists ExpirationLists	467200000
CY2020	us-gaap	Contract With Customer Liability Increase Decrease For Contract Acquired In Business Combination ContractWithCustomerLiabilityIncreaseDecreaseForContractAcquiredInBusinessCombination	9900000
CY2020Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	541300000
CY2020Q4	us-gaap	Finite Lived Noncompete Agreements Gross FiniteLivedNoncompeteAgreementsGross	11400000
CY2020Q4	us-gaap	Finite Lived Trade Names Gross FiniteLivedTradeNamesGross	12500000
CY2020Q4	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Assets BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets	1003500000
CY2020Q4	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Current Liabilities BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities	103600000
CY2020Q4	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Noncurrent Liabilities BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilities	23800000
CY2020Q4	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Liabilities BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities	127400000
CY2020Q4	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Net BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet	876100000
CY2020	us-gaap	Business Acquisitions Pro Forma Revenue BusinessAcquisitionsProFormaRevenue	7108700000
CY2019	us-gaap	Business Acquisitions Pro Forma Revenue BusinessAcquisitionsProFormaRevenue	7352700000
CY2020	ajg	Business Acquisitions Pro Forma Net Income Loss To Controlling Interest BusinessAcquisitionsProFormaNetIncomeLossToControllingInterest	817600000
CY2019	ajg	Business Acquisitions Pro Forma Net Income Loss To Controlling Interest BusinessAcquisitionsProFormaNetIncomeLossToControllingInterest	670500000
CY2020	us-gaap	Business Acquisition Pro Forma Earnings Per Share Basic BusinessAcquisitionProFormaEarningsPerShareBasic	4.26
CY2020Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	541300000
CY2019	us-gaap	Business Acquisition Pro Forma Earnings Per Share Basic BusinessAcquisitionProFormaEarningsPerShareBasic	3.57
CY2020	us-gaap	Business Acquisition Pro Forma Earnings Per Share Diluted BusinessAcquisitionProFormaEarningsPerShareDiluted	4.17
CY2019	us-gaap	Business Acquisition Pro Forma Earnings Per Share Diluted BusinessAcquisitionProFormaEarningsPerShareDiluted	3.49
CY2019	ajg	Net Change In Collected Billings And Deposits Received From Customers NetChangeInCollectedBillingsAndDepositsReceivedFromCustomers	-1100000
CY2019	ajg	Contract With Customer Impact Of Change In Foreign Exchange Rates ContractWithCustomerImpactOfChangeInForeignExchangeRates	1800000
CY2019	us-gaap	Contract With Customer Liability Increase Decrease For Contract Acquired In Business Combination ContractWithCustomerLiabilityIncreaseDecreaseForContractAcquiredInBusinessCombination	30600000
CY2019Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	503800000
CY2020	ajg	Contract With Customer Liability Additions ContractWithCustomerLiabilityAdditions	374000000.0
CY2020	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	382300000
CY2020	ajg	Net Change In Collected Billings And Deposits Received From Customers NetChangeInCollectedBillingsAndDepositsReceivedFromCustomers	25600000
CY2020	ajg	Contract With Customer Impact Of Change In Foreign Exchange Rates ContractWithCustomerImpactOfChangeInForeignExchangeRates	10300000
CY2020Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	541300000
CY2019Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	503800000
CY2018Q4	us-gaap	Contract With Customer Liability ContractWithCustomerLiability	457700000
CY2019	ajg	Contract With Customer Liability Additions ContractWithCustomerLiabilityAdditions	364300000
CY2019	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	349500000
CY2020Q4	us-gaap	Unbilled Contracts Receivable UnbilledContractsReceivable	603100000
CY2019Q4	us-gaap	Unbilled Contracts Receivable UnbilledContractsReceivable	556400000
CY2020Q4	us-gaap	Capitalized Contract Cost Net CapitalizedContractCostNet	102000000.0
CY2019Q4	us-gaap	Capitalized Contract Cost Net CapitalizedContractCostNet	98300000
CY2020Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	451200000
CY2020Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	54800000
CY2020Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	15600000
CY2020Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	7100000
CY2020Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	4400000
CY2020Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	8200000
CY2020Q4	us-gaap	Revenue Remaining Performance Obligation RevenueRemainingPerformanceObligation	541300000
CY2020Q4	us-gaap	Capitalized Contract Cost Net CapitalizedContractCostNet	102000000.0
CY2019Q4	us-gaap	Capitalized Contract Cost Net CapitalizedContractCostNet	98300000
CY2020Q4	us-gaap	Capitalized Contract Cost Accumulated Amortization CapitalizedContractCostAccumulatedAmortization	388400000
CY2019Q4	us-gaap	Capitalized Contract Cost Accumulated Amortization CapitalizedContractCostAccumulatedAmortization	355900000
CY2020Q4	ajg	Accrued Supplemental Direct Bill And Other Receivables Current AccruedSupplementalDirectBillAndOtherReceivablesCurrent	361700000
CY2019Q4	ajg	Accrued Supplemental Direct Bill And Other Receivables Current AccruedSupplementalDirectBillAndOtherReceivablesCurrent	369100000
CY2020Q4	us-gaap	Accounts Receivable Billed For Long Term Contracts Or Programs AccountsReceivableBilledForLongTermContractsOrPrograms	442700000
CY2019Q4	us-gaap	Accounts Receivable Billed For Long Term Contracts Or Programs AccountsReceivableBilledForLongTermContractsOrPrograms	388100000
CY2020Q4	ajg	Computer Equipment Gross ComputerEquipmentGross	214200000
CY2020Q4	ajg	Refined Coal Production Related Receivables Current RefinedCoalProductionRelatedReceivablesCurrent	95400000
CY2019Q4	ajg	Refined Coal Production Related Receivables Current RefinedCoalProductionRelatedReceivablesCurrent	103400000
CY2020Q4	us-gaap	Capitalized Contract Cost Net CapitalizedContractCostNet	102000000.0
CY2019Q4	us-gaap	Capitalized Contract Cost Net CapitalizedContractCostNet	98300000
CY2020Q4	us-gaap	Prepaid Expense Current PrepaidExpenseCurrent	112100000
CY2019Q4	us-gaap	Prepaid Expense Current PrepaidExpenseCurrent	115500000
CY2020Q4	us-gaap	Other Assets Current OtherAssetsCurrent	1113900000
CY2019Q4	us-gaap	Other Assets Current OtherAssetsCurrent	1074400000
CY2020Q4	us-gaap	Machinery And Equipment Gross MachineryAndEquipmentGross	33000000.0
CY2019Q4	us-gaap	Machinery And Equipment Gross MachineryAndEquipmentGross	32600000
CY2020Q4	us-gaap	Furniture And Fixtures Gross FurnitureAndFixturesGross	138300000
CY2019Q4	us-gaap	Furniture And Fixtures Gross FurnitureAndFixturesGross	126000000.0
CY2020Q4	us-gaap	Leasehold Improvements Gross LeaseholdImprovementsGross	166000000.0
CY2019Q4	us-gaap	Leasehold Improvements Gross LeaseholdImprovementsGross	150200000
CY2019Q4	ajg	Computer Equipment Gross ComputerEquipmentGross	176300000
CY2020Q4	ajg	Land And Buildings Gross LandAndBuildingsGross	145100000
CY2019Q4	ajg	Land And Buildings Gross LandAndBuildingsGross	144900000
CY2020Q4	us-gaap	Capitalized Computer Software Gross CapitalizedComputerSoftwareGross	452200000
CY2019Q4	us-gaap	Capitalized Computer Software Gross CapitalizedComputerSoftwareGross	392300000
CY2020Q4	us-gaap	Property Plant And Equipment Other PropertyPlantAndEquipmentOther	16700000
CY2019Q4	us-gaap	Property Plant And Equipment Other PropertyPlantAndEquipmentOther	19000000.0
CY2020Q4	us-gaap	Construction In Progress Gross ConstructionInProgressGross	14100000
CY2019Q4	us-gaap	Construction In Progress Gross ConstructionInProgressGross	18000000.0
CY2020Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	1179600000
CY2019Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	1059300000
CY2020Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	728900000
CY2019Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	591900000
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	450700000
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	467400000
CY2020Q4	us-gaap	Goodwill Goodwill	6127000000.0
CY2019Q4	us-gaap	Goodwill Goodwill	5618500000
CY2018Q4	us-gaap	Goodwill Goodwill	4625600000
CY2019	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	975700000
CY2019	us-gaap	Goodwill Written Off Related To Sale Of Business Unit GoodwillWrittenOffRelatedToSaleOfBusinessUnit	7200000
CY2019	us-gaap	Goodwill Translation And Purchase Accounting Adjustments GoodwillTranslationAndPurchaseAccountingAdjustments	24400000
CY2019Q4	us-gaap	Goodwill Goodwill	5618500000
CY2020	us-gaap	Goodwill Acquired During Period GoodwillAcquiredDuringPeriod	359600000
CY2020	us-gaap	Goodwill Purchase Accounting Adjustments GoodwillPurchaseAccountingAdjustments	31500000
CY2020	us-gaap	Goodwill Translation And Purchase Accounting Adjustments GoodwillTranslationAndPurchaseAccountingAdjustments	117400000
CY2020Q4	us-gaap	Goodwill Goodwill	6127000000.0
CY2020Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	2399900000
CY2019Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	2318700000
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	182700000
CY2020	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	4000000.0
CY2019Q4	us-gaap	Unamortized Debt Issuance Expense UnamortizedDebtIssuanceExpense	6900000
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	186000000.0
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	378400000
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	352300000
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	327100000
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	291300000
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Five FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	251300000
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense After Year Five FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive	799500000
CY2020Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	2399900000
CY2020Q4	ajg	Debt Long Term And Short Term Combined Amount Gross DebtLongTermAndShortTermCombinedAmountGross	4551600000
CY2019Q4	ajg	Debt Long Term And Short Term Combined Amount Gross DebtLongTermAndShortTermCombinedAmountGross	4613600000
CY2020Q4	us-gaap	Unamortized Debt Issuance Expense UnamortizedDebtIssuanceExpense	7000000.0
CY2020Q4	us-gaap	Debt Longterm And Shortterm Combined Amount DebtLongtermAndShorttermCombinedAmount	4544600000
CY2019Q4	us-gaap	Debt Longterm And Shortterm Combined Amount DebtLongtermAndShorttermCombinedAmount	4606700000
CY2020	us-gaap	Net Income Loss NetIncomeLoss	818800000
CY2019	us-gaap	Net Income Loss NetIncomeLoss	668800000
CY2018	us-gaap	Net Income Loss NetIncomeLoss	633500000
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	191000000.0
CY2019	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	4100000
CY2018	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	3500000
CY2020	ajg	Weighted Average Number Of Common And Common Equivalent Shares Outstanding WeightedAverageNumberOfCommonAndCommonEquivalentSharesOutstanding	195000000.0
CY2019	ajg	Weighted Average Number Of Common And Common Equivalent Shares Outstanding WeightedAverageNumberOfCommonAndCommonEquivalentSharesOutstanding	190100000
CY2018	ajg	Weighted Average Number Of Common And Common Equivalent Shares Outstanding WeightedAverageNumberOfCommonAndCommonEquivalentSharesOutstanding	186200000
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.29
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.60
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.47
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.20
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.52
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.40
CY2020	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0
CY2019	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	1000000.0
CY2018	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	1000000.0
CY2020	us-gaap	Stock Granted During Period Value Sharebased Compensation StockGrantedDuringPeriodValueSharebasedCompensation	13600000
CY2019	us-gaap	Stock Granted During Period Value Sharebased Compensation StockGrantedDuringPeriodValueSharebasedCompensation	14000000.0
CY2018	us-gaap	Stock Granted During Period Value Sharebased Compensation StockGrantedDuringPeriodValueSharebasedCompensation	13700000
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate	0.007
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	7900000
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	56.40
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	1600000
CY2020	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice	86.17
CY2020Q4	ajg	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Per Share ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendPerShare	2.1
CY2019Q4	ajg	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Per Share ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendPerShare	1.7
CY2018Q4	ajg	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Per Share ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendPerShare	2.3
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate	0.025
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate	0.027
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate	0.173
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate	0.156
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate	0.151
CY2020	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	1800000
CY2020	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	45.80
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod	200000
CY2020	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Forfeitures In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice	65.87
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	7500000
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	65.09
CY2020Q4	ajg	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Aggregate Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingAggregateIntrinsicValue	437900000
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber	1900000
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice	47.17
CY2020Q4	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Intrinsic Value1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1	147200000
CY2020Q4	ajg	Share Based Compensation Arrangement By Share Based Payment Award Options Non Vested And Expected To Vest Number Of Shares ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsNonVestedAndExpectedToVestNumberOfShares	5300000
CY2020Q4	ajg	Share Based Compensation Arrangement By Share Based Payment Award Options Nonvested And Expected To Vest Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsNonvestedAndExpectedToVestExercisableWeightedAverageExercisePrice	70.74
CY2020Q4	ajg	Sharebased Compensation Arrangement Non Vested And Expected To Vest Outstanding Aggregate Intrinsic Value SharebasedCompensationArrangementNonVestedAndExpectedToVestOutstandingAggregateIntrinsicValue	278100000
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	8800000
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	50.16
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	1300000
CY2019	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice	79.59
CY2019	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	1900000
CY2019	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	42.91
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod	300000
CY2019	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Forfeitures In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice	57.33
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	7900000
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	56.40
CY2019Q4	ajg	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Aggregate Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingAggregateIntrinsicValue	308600000
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber	2000000.0
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice	45.03
CY2019Q4	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Intrinsic Value1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1	101900000
CY2019Q4	ajg	Share Based Compensation Arrangement By Share Based Payment Award Options Non Vested And Expected To Vest Number Of Shares ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsNonVestedAndExpectedToVestNumberOfShares	5700000
CY2019Q4	ajg	Share Based Compensation Arrangement By Share Based Payment Award Options Nonvested And Expected To Vest Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsNonvestedAndExpectedToVestExercisableWeightedAverageExercisePrice	59.76
CY2019Q4	ajg	Sharebased Compensation Arrangement Non Vested And Expected To Vest Outstanding Aggregate Intrinsic Value SharebasedCompensationArrangementNonVestedAndExpectedToVestOutstandingAggregateIntrinsicValue	201500000
CY2019Q4	us-gaap	Defined Benefit Plan Funded Status Of Plan DefinedBenefitPlanFundedStatusOfPlan	-30700000
CY2019	ajg	Share Based Compensation Arrangement By Share Based Payment Award Options Exercised In Period Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisedInPeriodIntrinsicValue	54200000
CY2020Q4	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	28300000
CY2020	ajg	Weighted Average Period WeightedAveragePeriod	P4Y
CY2020	us-gaap	Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Lower Range Limit ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit	43.71
CY2020	us-gaap	Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Upper Range Limit ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit	86.17
CY2020Q4	us-gaap	Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Number Of Outstanding Options ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions	7500000
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	65.09
CY2020Q4	us-gaap	Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Number Of Exercisable Options ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions	1900000
CY2020Q4	us-gaap	Sharebased Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Exercisable Options Weighted Average Exercise Price1 SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1	47.17
CY2020	ajg	Deferred Equity Participation Plan Distributions To Key Executives Age DeferredEquityParticipationPlanDistributionsToKeyExecutivesAge	age 62 (or the one-year anniversary of the date of the grant for participants over the age of 61 as of the grant date) or upon or after their actual retirement if later.
CY2020	ajg	Deferred Equity Participation Sub Plan Distributions Requisite Service Description DeferredEquityParticipationSubPlanDistributionsRequisiteServiceDescription	we annually make awards under sub-plans of the DEPP for certain production staff, which generally provide for vesting and/or distributions no sooner than five years from the date of awards, although certain awards vest and/or distribute after the earlier of fifteen years or the participant reaching age 65.
CY2020	ajg	Deferred Equity Participation Sub Plan Distributions To Key Executives Age DeferredEquityParticipationSubPlanDistributionsToKeyExecutivesAge	age 65
CY2020	ajg	Share Based Compensation Arrangement By Share Based Payment Award Options Exercised In Period Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisedInPeriodIntrinsicValue	106400000
CY2018	ajg	Share Based Compensation Arrangement By Share Based Payment Award Options Exercised In Period Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisedInPeriodIntrinsicValue	77900000
CY2019Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	274400000
CY2018Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	253200000
CY2020	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	800000
CY2019	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	1600000
CY2020	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	8000000.0
CY2019	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	9800000
CY2020	us-gaap	Defined Benefit Plan Actuarial Gain Loss DefinedBenefitPlanActuarialGainLoss	-22600000
CY2019	us-gaap	Defined Benefit Plan Actuarial Gain Loss DefinedBenefitPlanActuarialGainLoss	-24700000
CY2020	us-gaap	Defined Benefit Plan Benefit Obligation Benefits Paid DefinedBenefitPlanBenefitObligationBenefitsPaid	15200000
CY2019	us-gaap	Defined Benefit Plan Benefit Obligation Benefits Paid DefinedBenefitPlanBenefitObligationBenefitsPaid	14900000
CY2020Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	290600000
CY2019Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	274400000
CY2019Q4	us-gaap	Defined Benefit Plan Fair Value Of Plan Assets DefinedBenefitPlanFairValueOfPlanAssets	243700000
CY2018Q4	us-gaap	Defined Benefit Plan Fair Value Of Plan Assets DefinedBenefitPlanFairValueOfPlanAssets	220000000.0
CY2020	us-gaap	Defined Benefit Plan Actual Return On Plan Assets DefinedBenefitPlanActualReturnOnPlanAssets	34300000
CY2019	us-gaap	Defined Benefit Plan Actual Return On Plan Assets DefinedBenefitPlanActualReturnOnPlanAssets	38600000
CY2020	us-gaap	Defined Benefit Plan Plan Assets Benefits Paid DefinedBenefitPlanPlanAssetsBenefitsPaid	15200000
CY2019	us-gaap	Defined Benefit Plan Plan Assets Benefits Paid DefinedBenefitPlanPlanAssetsBenefitsPaid	14900000
CY2020Q4	us-gaap	Defined Benefit Plan Fair Value Of Plan Assets DefinedBenefitPlanFairValueOfPlanAssets	262800000
CY2019Q4	us-gaap	Defined Benefit Plan Fair Value Of Plan Assets DefinedBenefitPlanFairValueOfPlanAssets	243700000
CY2020Q4	us-gaap	Defined Benefit Plan Funded Status Of Plan DefinedBenefitPlanFundedStatusOfPlan	-27800000
CY2018	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	-1000000.0
CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	-4700000
CY2018	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	9300000
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	-800000
CY2020Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent	27800000
CY2019Q4	us-gaap	Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent	30700000
CY2020Q4	us-gaap	Defined Benefit Plan Accumulated Other Comprehensive Income Net Gains Losses Before Tax DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax	-68300000
CY2019Q4	us-gaap	Defined Benefit Plan Accumulated Other Comprehensive Income Net Gains Losses Before Tax DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax	-69800000
CY2020Q4	ajg	Defined Benefit Plan Net Amount Included In Retained Earning DefinedBenefitPlanNetAmountIncludedInRetainedEarning	40500000
CY2019Q4	ajg	Defined Benefit Plan Net Amount Included In Retained Earning DefinedBenefitPlanNetAmountIncludedInRetainedEarning	39100000
CY2020	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	800000
CY2019	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	1600000
CY2018	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	800000
CY2020	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	8000000.0
CY2019	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	9800000
CY2020	us-gaap	Defined Benefit Plan Expected Return On Plan Assets DefinedBenefitPlanExpectedReturnOnPlanAssets	16400000
CY2019	us-gaap	Defined Benefit Plan Expected Return On Plan Assets DefinedBenefitPlanExpectedReturnOnPlanAssets	14800000
CY2018	us-gaap	Defined Benefit Plan Expected Return On Plan Assets DefinedBenefitPlanExpectedReturnOnPlanAssets	16000000.0
CY2020	us-gaap	Defined Benefit Plan Amortization Of Gains Losses DefinedBenefitPlanAmortizationOfGainsLosses	-6200000
CY2019	us-gaap	Defined Benefit Plan Amortization Of Gains Losses DefinedBenefitPlanAmortizationOfGainsLosses	-7000000.0
CY2018	us-gaap	Defined Benefit Plan Amortization Of Gains Losses DefinedBenefitPlanAmortizationOfGainsLosses	-4900000
CY2020	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	-1400000
CY2019	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	3600000
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax	-17200000
CY2020	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Before Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax	6200000
CY2019	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Before Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax	7000000.0
CY2018	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Before Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditBeforeTax	4900000
CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-1500000
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	-6200000
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax	12300000
CY2020	us-gaap	Amount Recognized In Net Periodic Benefit Cost And Other Comprehensive Income Loss Before Tax AmountRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeLossBeforeTax	-2900000
CY2019	us-gaap	Amount Recognized In Net Periodic Benefit Cost And Other Comprehensive Income Loss Before Tax AmountRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeLossBeforeTax	-2600000
CY2018	us-gaap	Amount Recognized In Net Periodic Benefit Cost And Other Comprehensive Income Loss Before Tax AmountRecognizedInNetPeriodicBenefitCostAndOtherComprehensiveIncomeLossBeforeTax	11300000
CY2020Q4	us-gaap	Defined Benefit Plan Expected Amortization Next Fiscal Year DefinedBenefitPlanExpectedAmortizationNextFiscalYear	5800000
CY2019Q4	us-gaap	Defined Benefit Plan Expected Amortization Next Fiscal Year DefinedBenefitPlanExpectedAmortizationNextFiscalYear	6100000
CY2018Q4	us-gaap	Defined Benefit Plan Expected Amortization Next Fiscal Year DefinedBenefitPlanExpectedAmortizationNextFiscalYear	7200000
CY2020Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate	0.0225
CY2019Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate	0.0300
CY2020	ajg	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Expected Long Term Return On Plan Assets DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationExpectedLongTermReturnOnPlanAssets	0.0700
CY2019	ajg	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Expected Long Term Return On Plan Assets DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationExpectedLongTermReturnOnPlanAssets	0.0700
CY2020	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate	0.0300
CY2019	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate	0.0400
CY2018	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate	0.0350
CY2020	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets	0.0700
CY2019	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets	0.0700
CY2018	us-gaap	Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Expected Long Term Return On Assets DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets	0.0700
CY2019Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Next Twelve Months DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths	16200000
CY2019Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Two DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo	16500000
CY2019Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Three DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree	16700000
CY2019Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Four DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour	16700000
CY2019Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Year Five DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive	16900000
CY2019Q4	us-gaap	Defined Benefit Plan Expected Future Benefit Payments Five Fiscal Years Thereafter DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter	83100000
CY2020Q4	us-gaap	Defined Benefit Plan Weighted Average Asset Allocations DefinedBenefitPlanWeightedAverageAssetAllocations	1.000
CY2019Q4	us-gaap	Defined Benefit Plan Weighted Average Asset Allocations DefinedBenefitPlanWeightedAverageAssetAllocations	1.000
CY2020Q4	us-gaap	Defined Benefit Plan Fair Value Of Plan Assets DefinedBenefitPlanFairValueOfPlanAssets	262800000
CY2019Q4	us-gaap	Defined Benefit Plan Fair Value Of Plan Assets DefinedBenefitPlanFairValueOfPlanAssets	243700000
CY2020	us-gaap	Defined Benefit Plan Contributions By Employer DefinedBenefitPlanContributionsByEmployer	0
CY2019	us-gaap	Defined Benefit Plan Contributions By Employer DefinedBenefitPlanContributionsByEmployer	0
CY2018	us-gaap	Defined Benefit Plan Contributions By Employer DefinedBenefitPlanContributionsByEmployer	0
CY2019	us-gaap	Defined Contribution Plan Employer Discretionary Contribution Amount DefinedContributionPlanEmployerDiscretionaryContributionAmount	30000000.0
CY2019	us-gaap	Direct Premiums Written DirectPremiumsWritten	44600000
CY2019	us-gaap	Direct Premiums Earned DirectPremiumsEarned	59100000
CY2020	us-gaap	Defined Contribution Plan Employer Discretionary Contribution Amount DefinedContributionPlanEmployerDiscretionaryContributionAmount	0
CY2018	us-gaap	Defined Contribution Plan Employer Discretionary Contribution Amount DefinedContributionPlanEmployerDiscretionaryContributionAmount	0
CY2020Q4	us-gaap	Equity Method Investments EquityMethodInvestments	22400000
CY2020Q4	ajg	Equity Method Investment Summarized Financial Information Funding Commitments EquityMethodInvestmentSummarizedFinancialInformationFundingCommitments	900000
CY2019Q4	us-gaap	Equity Method Investments EquityMethodInvestments	40000000.0
CY2020Q4	ajg	Number Of Certified Low Income Housing Developments Investment NumberOfCertifiedLowIncomeHousingDevelopmentsInvestment	8
CY2020	us-gaap	Lease Cost LeaseCost	147400000
CY2020	ajg	Operating Leases Cash Flow Related Information OperatingLeasesCashFlowRelatedInformation	<p style="text-align:left;margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;"> </p> <div> <table border="0" cellpadding="0" cellspacing="0" style="margin:auto;border-collapse:collapse; width:100%;"> <tr> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:73.02%;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;;font-size:12pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:2.06%;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;color:#000000;font-size:8pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td colspan="2" style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:23.9%;" valign="bottom"> <p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;color:#000000;font-size:8pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">Year ended</p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1%;white-space:nowrap;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;color:#000000;font-size:8pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> </tr> <tr> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:73.02%; border-bottom:solid 0.75pt #000000;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;color:#000000;font-size:8pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">Supplemental Cash Flow Information Related to Leases (in millions)</p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:2.06%; border-bottom:solid 0.75pt transparent;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;color:#000000;font-size:8pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td colspan="2" style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:23.9%; border-bottom:solid 0.75pt #000000;" valign="bottom"> <p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;color:#000000;font-size:8pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">December 31, 2020</p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:1%;white-space:nowrap;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;color:#000000;font-size:8pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> </tr> <tr> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:73.02%; border-top:solid 0.75pt #000000;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">Cash paid for amounts included in the measurement of</p> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> lease liabilities:</p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:2.06%;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1%; border-top:solid 0.75pt #000000;white-space:nowrap;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:22.9%; border-top:solid 0.75pt #000000;white-space:nowrap;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1%;white-space:nowrap;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> </tr> <tr> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:73.02%;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:13.7pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">Operating cash flows from operating leases</p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:2.06%;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1%;white-space:nowrap;" valign="middle"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">$</p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:22.9%;white-space:nowrap;" valign="middle"> <p style="text-align:right;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">120.1</p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1%;white-space:nowrap;" valign="middle"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> </tr> <tr> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:73.02%;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">Right-of-use assets obtained in exchange for new</p> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> operating lease liabilities</p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:2.06%;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1%;white-space:nowrap;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">$</p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:22.9%;white-space:nowrap;" valign="bottom"> <p style="text-align:right;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">71.2</p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1%;white-space:nowrap;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:1pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> </tr> </table></div> <p style="text-align:left;margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;"> </p>
CY2020	us-gaap	Operating Lease Payments OperatingLeasePayments	120100000
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	71200000
CY2020	ajg	Operating Lease Related Assets And Liabilities And Other Related Information OperatingLeaseRelatedAssetsAndLiabilitiesAndOtherRelatedInformation	<p style="text-align:left;margin-bottom:0pt;margin-top:12pt;text-indent:0%;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">Supplemental balance sheet information related to leases is as follows (in millions, except lease term and discount rate):</p> <p style="text-align:left;margin-bottom:0pt;margin-top:0pt;text-indent:0%;font-family:Times New Roman;font-size:10pt;"> </p> <div> <table border="0" cellpadding="0" cellspacing="0" style="margin:auto;border-collapse:collapse; width:100%;"> <tr> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:39.4%; border-bottom:solid 0.75pt #000000;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;color:#000000;font-size:8pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">Lease Components</p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:1.9%; border-bottom:solid 0.75pt transparent;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;color:#000000;font-size:8pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:39.4%; border-bottom:solid 0.75pt #000000;" valign="bottom"> <p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;color:#000000;font-size:8pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">Balance Sheet Classification</p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:1.9%; border-bottom:solid 0.75pt transparent;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;color:#000000;font-size:8pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td colspan="2" style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:16.34%; border-bottom:solid 0.75pt #000000;" valign="bottom"> <p style="text-align:center;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;color:#000000;font-size:8pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;">December 31, 2020</p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:1%;white-space:nowrap;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;font-weight:bold;color:#000000;font-size:8pt;font-family:Times New Roman;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> </tr> <tr> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:39.4%; border-top:solid 0.75pt #000000; border-bottom:double 2.5pt transparent;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">Lease right-of-use assets</p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:1.9%; border-bottom:double 2.5pt transparent;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:39.4%; border-top:solid 0.75pt #000000; border-bottom:double 2.5pt transparent;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">Right-of-use assets</p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:1.9%; border-bottom:double 2.5pt transparent;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1%; border-top:solid 0.75pt #000000; border-bottom:double 2.5pt #000000;white-space:nowrap;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">$</p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:15.34%; border-top:solid 0.75pt #000000; border-bottom:double 2.5pt #000000;white-space:nowrap;" valign="bottom"> <p style="text-align:right;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">373.9</p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:1%; border-bottom:double 2.5pt transparent;white-space:nowrap;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> </tr> <tr> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:39.4%;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">Other current lease liabilities</p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1.9%;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:39.4%;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">Accrued compensation and other current liabilities</p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1.9%;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1%; border-top:double 2.5pt #000000;white-space:nowrap;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:15.34%; border-top:double 2.5pt #000000;white-space:nowrap;" valign="bottom"> <p style="text-align:right;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">88.8</p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1%;white-space:nowrap;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> </tr> <tr> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:39.4%; border-bottom:solid 0.75pt transparent;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">Lease liabilities</p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:1.9%; border-bottom:solid 0.75pt transparent;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:39.4%; border-bottom:solid 0.75pt transparent;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">Lease liabilities - noncurrent</p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:1.9%; border-bottom:solid 0.75pt transparent;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1%; border-bottom:solid 0.75pt #000000;white-space:nowrap;" valign="middle"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:15.34%; border-bottom:solid 0.75pt #000000;white-space:nowrap;" valign="middle"> <p style="text-align:right;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">320.9</p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:1%; border-bottom:solid 0.75pt transparent;white-space:nowrap;" valign="middle"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> </tr> <tr> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:39.4%; border-bottom:double 2.5pt transparent;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:13.7pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">Total lease liabilities</p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:1.9%; border-bottom:double 2.5pt transparent;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:39.4%; border-bottom:double 2.5pt transparent;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:1.9%; border-bottom:double 2.5pt transparent;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1%; border-top:solid 0.75pt #000000; border-bottom:double 2.5pt #000000;white-space:nowrap;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">$</p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:15.34%; border-top:solid 0.75pt #000000; border-bottom:double 2.5pt #000000;white-space:nowrap;" valign="bottom"> <p style="text-align:right;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">409.7</p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;width:1%; border-bottom:double 2.5pt transparent;white-space:nowrap;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> </tr> <tr> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:39.4%;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">Weighted-average remaining lease term, years</p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1.9%;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:39.4%;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1.9%;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1%; border-top:double 2.5pt #000000;white-space:nowrap;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:15.34%; border-top:double 2.5pt #000000;white-space:nowrap;" valign="bottom"> <p style="text-align:right;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"><span style="-sec-ix-hidden:F_001904">5.3</span></p></td> <td style="background-color:#CFF0FC;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1%;white-space:nowrap;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> </tr> <tr> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:39.4%;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">Weighted-average discount rate</p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1.9%;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:39.4%;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1.9%;" valign="top"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1%;white-space:nowrap;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;"> </p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:15.34%;white-space:nowrap;" valign="bottom"> <p style="text-align:right;margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">3.6</p></td> <td style="background-color:#FFFFFF;padding-left:0pt;padding-Right:0.75pt;padding-Top:0.75pt;padding-Bottom:0pt;width:1%;white-space:nowrap;" valign="bottom"> <p style="margin-bottom:0pt;margin-top:0pt;margin-left:0pt;;text-indent:0pt;;color:#000000;font-size:10pt;font-family:Times New Roman;font-weight:normal;font-style:normal;text-transform:none;font-variant: normal;">%</p></td> </tr> </table></div>
CY2020Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	373900000
CY2020Q4	us-gaap	Operating Lease Liability Current OperatingLeaseLiabilityCurrent	88800000
CY2020Q4	us-gaap	Operating Lease Liability Noncurrent OperatingLeaseLiabilityNoncurrent	320900000
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	409700000
CY2020Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.036
CY2018	us-gaap	Direct Premiums Written DirectPremiumsWritten	57600000
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	108500000
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	93900000
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	75100000
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	54800000
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	41600000
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	77800000
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	451700000
CY2020Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	42000000.0
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	409700000
CY2020	us-gaap	Lessee Operating Lease Option To Extend LesseeOperatingLeaseOptionToExtend	5.0 years
CY2020Q4	ajg	Operating Lease Liability Not Yet Commenced OperatingLeaseLiabilityNotYetCommenced	300000
CY2020Q4	us-gaap	Derivative Notional Amount DerivativeNotionalAmount	598600000
CY2020Q4	us-gaap	Derivative Asset Notional Amount DerivativeAssetNotionalAmount	13700000
CY2020Q4	us-gaap	Derivative Liability Notional Amount DerivativeLiabilityNotionalAmount	69300000
CY2019Q4	us-gaap	Derivative Notional Amount DerivativeNotionalAmount	831700000
CY2019Q4	us-gaap	Derivative Asset Notional Amount DerivativeAssetNotionalAmount	21200000
CY2019Q4	us-gaap	Derivative Liability Notional Amount DerivativeLiabilityNotionalAmount	52400000
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationBeforeTax	-97100000
CY2020	us-gaap	Derivative Instruments Gain Loss Reclassified From Accumulated Oci Into Income Effective Portion Net DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet	-6300000
CY2020	ajg	Amount Of Gain Loss Recognized Effectiveness Testing AmountOfGainLossRecognizedEffectivenessTesting	2300000
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationBeforeTax	-37100000
CY2019	us-gaap	Derivative Instruments Gain Loss Reclassified From Accumulated Oci Into Income Effective Portion Net DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet	-5200000
CY2019	ajg	Amount Of Gain Loss Recognized Effectiveness Testing AmountOfGainLossRecognizedEffectivenessTesting	1300000
CY2020Q4	ajg	Number Of Square Feet NumberOfSquareFeet	360000
CY2020	ajg	Number Of Employees NumberOfEmployees	2000
CY2020	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	154000000.0
CY2019	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	148100000
CY2018	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	140000000.0
CY2020	ajg	Amount Of Commitment Expiration Off Balance Sheet Commitments Within Year One AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearOne	200000
CY2020	ajg	Amount Of Commitment Expiration Off Balance Sheet Commitments Within Year Two AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearTwo	200000
CY2020	ajg	Amount Of Commitment Expiration Off Balance Sheet Commitments Within Year Three AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearThree	200000
CY2020	ajg	Amount Of Commitment Expiration Off Balance Sheet Commitments Within Year Four AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearFour	200000
CY2020	ajg	Amount Of Commitment Expiration Off Balance Sheet Commitments Within Year Five AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearFive	200000
CY2020	ajg	Amount Of Commitment Expiration Off Balance Sheet Commitments Within Year Thereafter AmountOfCommitmentExpirationOffBalanceSheetCommitmentsWithinYearThereafter	18600000
CY2020	ajg	Amount Of Commitment Expiration Off Balance Sheet Commitments AmountOfCommitmentExpirationOffBalanceSheetCommitments	19600000
	us-gaap	Number Of Businesses Acquired NumberOfBusinessesAcquired	583
CY2020	ajg	Business Combination Aggregate Earnout Obligation Maximum BusinessCombinationAggregateEarnoutObligationMaximum	1128100000
CY2020	ajg	Business Combination Aggregate Earnout Obligation Recorded Maximum BusinessCombinationAggregateEarnoutObligationRecordedMaximum	592200000
CY2020Q4	ajg	Business Combination Aggregate Earnout Obligation Expected Settlement In Cash Or Stock At Option BusinessCombinationAggregateEarnoutObligationExpectedSettlementInCashOrStockAtOption	493700000
CY2020Q4	ajg	Business Combination Aggregate Earnout Obligation Expected Settlement In Cash BusinessCombinationAggregateEarnoutObligationExpectedSettlementInCash	98500000
CY2020Q4	us-gaap	Long Term Debt LongTermDebt	19600000
CY2020Q4	ajg	Liabilities Recorded On Self Insurance LiabilitiesRecordedOnSelfInsurance	17500000
CY2020	us-gaap	Income Tax Credits And Adjustments IncomeTaxCreditsAndAdjustments	108000000.0
CY2020	us-gaap	Direct Premiums Written DirectPremiumsWritten	37700000
CY2020	us-gaap	Direct Premiums Earned DirectPremiumsEarned	40700000
CY2019	us-gaap	Ceded Premiums Earned CededPremiumsEarned	61000000.0
CY2018	us-gaap	Direct Premiums Earned DirectPremiumsEarned	53200000
CY2020	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	100000
CY2020	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	900000
CY2019	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	1000000.0
CY2019	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	1900000
CY2018	us-gaap	Assumed Premiums Written AssumedPremiumsWritten	4700000
CY2018	us-gaap	Assumed Premiums Earned AssumedPremiumsEarned	4600000
CY2020	us-gaap	Ceded Premiums Written CededPremiumsWritten	37800000
CY2020	us-gaap	Ceded Premiums Earned CededPremiumsEarned	41600000
CY2019	us-gaap	Ceded Premiums Written CededPremiumsWritten	45600000
CY2018	us-gaap	Ceded Premiums Written CededPremiumsWritten	62300000
CY2018	us-gaap	Ceded Premiums Earned CededPremiumsEarned	57800000
CY2020Q4	us-gaap	Reinsurance Recoverables ReinsuranceRecoverables	48500000
CY2019Q4	us-gaap	Reinsurance Recoverables ReinsuranceRecoverables	45700000
CY2020	us-gaap	Interest Expense Domestic Deposits InterestExpenseDomesticDeposits	24000000.0
CY2019	us-gaap	Interest Expense Domestic Deposits InterestExpenseDomesticDeposits	40100000
CY2018	us-gaap	Interest Expense Domestic Deposits InterestExpenseDomesticDeposits	65800000
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	524400000
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	388400000
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Domestic IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic	337600000
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	346500000
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	237700000
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Foreign IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign	141800000
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	870900000
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	626100000
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	479400000
CY2020	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	43600000
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	3800000
CY2020	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-112400000
CY2019	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-142500000
CY2018	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-214000000.0
CY2020	us-gaap	Federal Income Tax Expense Benefit Continuing Operations FederalIncomeTaxExpenseBenefitContinuingOperations	-68800000
CY2019	us-gaap	Federal Income Tax Expense Benefit Continuing Operations FederalIncomeTaxExpenseBenefitContinuingOperations	-138700000
CY2018	us-gaap	Federal Income Tax Expense Benefit Continuing Operations FederalIncomeTaxExpenseBenefitContinuingOperations	-214000000.0
CY2020	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	36600000
CY2019	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	11100000
CY2018	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	15400000
CY2020	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-19300000
CY2019	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-6000000.0
CY2018	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-29000000.0
CY2020	us-gaap	State And Local Income Tax Expense Benefit Continuing Operations StateAndLocalIncomeTaxExpenseBenefitContinuingOperations	17300000
CY2019	us-gaap	State And Local Income Tax Expense Benefit Continuing Operations StateAndLocalIncomeTaxExpenseBenefitContinuingOperations	5100000
CY2018	us-gaap	State And Local Income Tax Expense Benefit Continuing Operations StateAndLocalIncomeTaxExpenseBenefitContinuingOperations	-13600000
CY2020	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	94600000
CY2019	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	66600000
CY2018	us-gaap	Current Foreign Tax Expense Benefit CurrentForeignTaxExpenseBenefit	60700000
CY2020	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-30300000
CY2019	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-22700000
CY2018	us-gaap	Deferred Foreign Income Tax Expense Benefit DeferredForeignIncomeTaxExpenseBenefit	-29600000
CY2020	us-gaap	Foreign Income Tax Expense Benefit Continuing Operations ForeignIncomeTaxExpenseBenefitContinuingOperations	64300000
CY2019	us-gaap	Foreign Income Tax Expense Benefit Continuing Operations ForeignIncomeTaxExpenseBenefitContinuingOperations	43900000
CY2018	us-gaap	Foreign Income Tax Expense Benefit Continuing Operations ForeignIncomeTaxExpenseBenefitContinuingOperations	31100000
CY2019	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2018	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	100700000
CY2018	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2020	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	22200000
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Foreign Income Tax Rate Differential EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential	-0.003
CY2020	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.026
CY2018	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.018
CY2020	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	-2500000
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	12800000
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-89700000
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-196500000
CY2020	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	182900000
CY2020	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2019	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	131500000
CY2019	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	4400000
CY2019	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.007
CY2018	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	8500000
CY2019	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	-10100000
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Foreign Income Tax Rate Differential EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential	-0.016
CY2018	us-gaap	Income Tax Reconciliation Foreign Income Tax Rate Differential IncomeTaxReconciliationForeignIncomeTaxRateDifferential	-14800000
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Foreign Income Tax Rate Differential EffectiveIncomeTaxRateReconciliationForeignIncomeTaxRateDifferential	-0.031
CY2020	us-gaap	Income Tax Reconciliation Tax Credits IncomeTaxReconciliationTaxCredits	154300000
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits EffectiveIncomeTaxRateReconciliationTaxCredits	0.177
CY2019	us-gaap	Income Tax Reconciliation Tax Credits IncomeTaxReconciliationTaxCredits	196100000
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits EffectiveIncomeTaxRateReconciliationTaxCredits	0.313
CY2018	us-gaap	Income Tax Reconciliation Tax Credits IncomeTaxReconciliationTaxCredits	252900000
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Tax Credits EffectiveIncomeTaxRateReconciliationTaxCredits	0.528
CY2020	ajg	Income Tax Reconciliation Other Permanent Differences IncomeTaxReconciliationOtherPermanentDifferences	-15700000
CY2020	ajg	Effective Income Tax Rate Reconciliation Other Permanent Differences EffectiveIncomeTaxRateReconciliationOtherPermanentDifferences	-0.018
CY2019	ajg	Income Tax Reconciliation Other Permanent Differences IncomeTaxReconciliationOtherPermanentDifferences	-7600000
CY2019	ajg	Effective Income Tax Rate Reconciliation Other Permanent Differences EffectiveIncomeTaxRateReconciliationOtherPermanentDifferences	-0.012
CY2018	ajg	Income Tax Reconciliation Other Permanent Differences IncomeTaxReconciliationOtherPermanentDifferences	900000
CY2018	ajg	Effective Income Tax Rate Reconciliation Other Permanent Differences EffectiveIncomeTaxRateReconciliationOtherPermanentDifferences	0.002
CY2018	ajg	Increase Decrease In Income Taxes Reconciliation Repatriation Of Foreign Earnings IncreaseDecreaseInIncomeTaxesReconciliationRepatriationOfForeignEarnings	-1800000
CY2018	ajg	Increase Decrease In Effective Income Tax Rate Reconciliation Repatriation Of Foreign Earnings IncreaseDecreaseInEffectiveIncomeTaxRateReconciliationRepatriationOfForeignEarnings	-0.004
CY2020	us-gaap	Income Tax Reconciliation Nondeductible Expense Share Based Compensation Cost IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost	-31400000
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense Share Based Compensation Cost EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost	-0.036
CY2019	us-gaap	Income Tax Reconciliation Nondeductible Expense Share Based Compensation Cost IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost	-16200000
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense Share Based Compensation Cost EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost	-0.026
CY2018	us-gaap	Income Tax Reconciliation Nondeductible Expense Share Based Compensation Cost IncomeTaxReconciliationNondeductibleExpenseShareBasedCompensationCost	-15000000.0
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Nondeductible Expense Share Based Compensation Cost EffectiveIncomeTaxRateReconciliationNondeductibleExpenseShareBasedCompensationCost	-0.031
CY2019	ajg	Income Tax Reconciliation Changes In Unrecognized Tax Benefits Related To Resolution Of Federal And State Audits Expiration Of Various Statutes Of Limitations And Other Items IncomeTaxReconciliationChangesInUnrecognizedTaxBenefitsRelatedToResolutionOfFederalAndStateAuditsExpirationOfVariousStatutesOfLimitationsAndOtherItems	800000
CY2019	ajg	Effective Income Tax Rate Reconciliation Changes In Unrecognized Tax Benefits Related To Resolution Of Federal And State Audits Expiration Of Various Statutes Of Limitations And Other Items EffectiveIncomeTaxRateReconciliationChangesInUnrecognizedTaxBenefitsRelatedToResolutionOfFederalAndStateAuditsExpirationOfVariousStatutesOfLimitationsAndOtherItems	0.001
CY2018	ajg	Income Tax Reconciliation Changes In Unrecognized Tax Benefits Related To Resolution Of Federal And State Audits Expiration Of Various Statutes Of Limitations And Other Items IncomeTaxReconciliationChangesInUnrecognizedTaxBenefitsRelatedToResolutionOfFederalAndStateAuditsExpirationOfVariousStatutesOfLimitationsAndOtherItems	-200000
CY2020	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	6500000
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Change In Deferred Tax Assets Valuation Allowance EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance	0.007
CY2019	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	7500000
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Change In Deferred Tax Assets Valuation Allowance EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance	0.012
CY2018	us-gaap	Income Tax Reconciliation Change In Deferred Tax Assets Valuation Allowance IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance	-22000000.0
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Change In Deferred Tax Assets Valuation Allowance EffectiveIncomeTaxRateReconciliationChangeInDeferredTaxAssetsValuationAllowance	-0.046
CY2020	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	5500000
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Change In Enacted Tax Rate EffectiveIncomeTaxRateReconciliationChangeInEnactedTaxRate	0.006
CY2019	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	-3700000
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Change In Enacted Tax Rate EffectiveIncomeTaxRateReconciliationChangeInEnactedTaxRate	-0.006
CY2020	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-400000
CY2019	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-200000
CY2018	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	100000
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	12800000
CY2020	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.015
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-89700000
CY2019	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	-0.143
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-196500000
CY2018	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	-0.410
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	11500000
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	10700000
CY2020	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	2900000
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	2100000
CY2020	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	1100000
CY2019	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	400000
CY2020	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	1200000
CY2019	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	1100000
CY2020	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	200000
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	600000
CY2020	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	1100000
CY2019	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	400000
CY2020Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	11200000
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	11500000
CY2020Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	9500000
CY2019Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	9400000
CY2020Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	3000000.0
CY2019Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued	3100000
CY2020Q4	ajg	Deferred Tax Assets Alternative Minimum Tax And Other Credit Carryforwards DeferredTaxAssetsAlternativeMinimumTaxAndOtherCreditCarryforwards	998000000.0
CY2019Q4	ajg	Deferred Tax Assets Alternative Minimum Tax And Other Credit Carryforwards DeferredTaxAssetsAlternativeMinimumTaxAndOtherCreditCarryforwards	962100000
CY2020Q4	ajg	Deferred Tax Assets Accrued And Unfunded Compensation And Employee Benefits DeferredTaxAssetsAccruedAndUnfundedCompensationAndEmployeeBenefits	239900000
CY2019Q4	ajg	Deferred Tax Assets Accrued And Unfunded Compensation And Employee Benefits DeferredTaxAssetsAccruedAndUnfundedCompensationAndEmployeeBenefits	156000000.0
CY2020Q4	us-gaap	Deferred Tax Assets Goodwill And Intangible Assets DeferredTaxAssetsGoodwillAndIntangibleAssets	61300000
CY2019Q4	us-gaap	Deferred Tax Assets Goodwill And Intangible Assets DeferredTaxAssetsGoodwillAndIntangibleAssets	54300000
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	14400000
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	11300000
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Accrued Liabilities DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities	65700000
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Accrued Liabilities DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities	63900000
CY2020Q4	ajg	Deferred Tax Assets Accrued Pension Liability DeferredTaxAssetsAccruedPensionLiability	9300000
CY2019Q4	ajg	Deferred Tax Assets Accrued Pension Liability DeferredTaxAssetsAccruedPensionLiability	9900000
CY2020Q4	us-gaap	Deferred Tax Assets Investments DeferredTaxAssetsInvestments	1300000
CY2019Q4	us-gaap	Deferred Tax Assets Investments DeferredTaxAssetsInvestments	900000
CY2020Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	36100000
CY2019Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	37200000
CY2020Q4	us-gaap	Deferred Tax Assets Capital Loss Carryforwards DeferredTaxAssetsCapitalLossCarryforwards	9000000.0
CY2019Q4	us-gaap	Deferred Tax Assets Capital Loss Carryforwards DeferredTaxAssetsCapitalLossCarryforwards	12600000
CY2020Q4	ajg	Deferred Tax Assets Lease Liabilities DeferredTaxAssetsLeaseLiabilities	96300000
CY2019Q4	ajg	Deferred Tax Assets Lease Liabilities DeferredTaxAssetsLeaseLiabilities	65300000
CY2020Q4	us-gaap	Deferred Tax Assets Hedging Transactions DeferredTaxAssetsHedgingTransactions	34600000
CY2019Q4	us-gaap	Deferred Tax Assets Hedging Transactions DeferredTaxAssetsHedgingTransactions	11700000
CY2020Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	2800000
CY2019Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	4300000
CY2020Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	1568700000
CY2019Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	1389500000
CY2020Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	94900000
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	80500000
CY2020Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	1473800000
CY2019Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	1309000000.0
CY2020Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	316900000
CY2019Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	322400000
CY2020Q4	ajg	Deferred Tax Liabilities Investment Related Partnerships DeferredTaxLiabilitiesInvestmentRelatedPartnerships	8500000
CY2019Q4	ajg	Deferred Tax Liabilities Investment Related Partnerships DeferredTaxLiabilitiesInvestmentRelatedPartnerships	9100000
CY2020Q4	ajg	Deferred Tax Liabilities Depreciable Fixed Assets DeferredTaxLiabilitiesDepreciableFixedAssets	32400000
CY2019Q4	ajg	Deferred Tax Liabilities Depreciable Fixed Assets DeferredTaxLiabilitiesDepreciableFixedAssets	22400000
CY2020Q4	ajg	Deferred Tax Liabilities Right Of Use Asset DeferredTaxLiabilitiesRightOfUseAsset	92200000
CY2019Q4	ajg	Deferred Tax Liabilities Right Of Use Asset DeferredTaxLiabilitiesRightOfUseAsset	62600000
CY2020Q4	ajg	Deferred Tax Liabilities Revenue Recognition DeferredTaxLiabilitiesRevenueRecognition	33100000
CY2019Q4	ajg	Deferred Tax Liabilities Revenue Recognition DeferredTaxLiabilitiesRevenueRecognition	63700000
CY2020Q4	ajg	Deferred Tax Liabilities Other Prepaid Items DeferredTaxLiabilitiesOtherPrepaidItems	12000000.0
CY2019Q4	ajg	Deferred Tax Liabilities Other Prepaid Items DeferredTaxLiabilitiesOtherPrepaidItems	10600000
CY2020Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	495100000
CY2019Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	490800000
CY2020Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	978700000
CY2019Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	818200000
CY2020Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	36100000
CY2020	ajg	Deferred Tax Assets Operating Loss Carryforward Expiration Year DeferredTaxAssetsOperatingLossCarryforwardExpirationYear	2023
CY2020Q4	us-gaap	Deferred Tax Liabilities Undistributed Foreign Earnings DeferredTaxLiabilitiesUndistributedForeignEarnings	658900000
CY2019Q4	us-gaap	Deferred Tax Liabilities Undistributed Foreign Earnings DeferredTaxLiabilitiesUndistributedForeignEarnings	574000000.0
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Employee Compensation DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeCompensation	12900000
CY2020	us-gaap	Interest Paid InterestPaid	188900000
CY2019	us-gaap	Interest Paid InterestPaid	169200000
CY2018	us-gaap	Interest Paid InterestPaid	139200000
CY2020	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	113000000.0
CY2019	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	22200000
CY2018	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	68100000
CY2020	us-gaap	Proceeds From Income Tax Refunds ProceedsFromIncomeTaxRefunds	28500000
CY2019	us-gaap	Proceeds From Income Tax Refunds ProceedsFromIncomeTaxRefunds	63600000
CY2018	us-gaap	Proceeds From Income Tax Refunds ProceedsFromIncomeTaxRefunds	2400000
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	604800000
CY2018Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	607200000
CY2020Q4	us-gaap	Restricted Cash Current RestrictedCashCurrent	2909700000
CY2019Q4	us-gaap	Restricted Cash Current RestrictedCashCurrent	2019100000
CY2018Q4	us-gaap	Restricted Cash Current RestrictedCashCurrent	1629600000
CY2020Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	664600000
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	3574300000
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	2623900000
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	2236800000
CY2020	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	6100000
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	7000000.0
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax	4900000
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	6300000
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	5200000
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	5700000
CY2019	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Reclassification Adjustment From Aoci Realized Upon Sale Or Liquidation Before Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentFromAOCIRealizedUponSaleOrLiquidationBeforeTax	0
CY2018	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Reclassification Adjustment From Aoci Realized Upon Sale Or Liquidation Before Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentFromAOCIRealizedUponSaleOrLiquidationBeforeTax	0
CY2020	us-gaap	Other Comprehensive Income Loss Foreign Currency Transaction And Translation Reclassification Adjustment From Aoci Realized Upon Sale Or Liquidation Before Tax OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentFromAOCIRealizedUponSaleOrLiquidationBeforeTax	0
CY2020Q1	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1866900000
CY2020Q2	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1584000000.0
CY2020Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1849100000
CY2020Q4	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1703600000
CY2020Q1	us-gaap	Costs And Expenses CostsAndExpenses	1510900000
CY2020Q2	us-gaap	Costs And Expenses CostsAndExpenses	1412300000
CY2020Q3	us-gaap	Costs And Expenses CostsAndExpenses	1639600000
CY2020Q4	us-gaap	Costs And Expenses CostsAndExpenses	1569900000
CY2020Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	356000000.0
CY2020Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	171700000
CY2020Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	209500000
CY2020Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	133700000
CY2020Q1	us-gaap	Net Income Loss NetIncomeLoss	346300000
CY2020Q2	us-gaap	Net Income Loss NetIncomeLoss	153700000
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	176600000
CY2020Q4	us-gaap	Net Income Loss NetIncomeLoss	142200000
CY2020Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.83
CY2020Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.81
CY2020Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.92
CY2020Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.74
CY2020Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.79
CY2020Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.79
CY2020Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.90
CY2020Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.72
CY2019Q1	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1990600000
CY2019Q2	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1657800000
CY2019Q3	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1825200000
CY2019Q4	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	1721400000
CY2019Q1	us-gaap	Costs And Expenses CostsAndExpenses	1668800000
CY2019Q2	us-gaap	Costs And Expenses CostsAndExpenses	1552300000
CY2019Q3	us-gaap	Costs And Expenses CostsAndExpenses	1710400000
CY2019Q4	us-gaap	Costs And Expenses CostsAndExpenses	1637400000
CY2019Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	321800000
CY2019Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	105500000
CY2019Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	114800000
CY2019Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	84000000.0
CY2019Q1	us-gaap	Net Income Loss NetIncomeLoss	334100000
CY2019Q2	us-gaap	Net Income Loss NetIncomeLoss	110100000
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	126100000
CY2019Q4	us-gaap	Net Income Loss NetIncomeLoss	98500000
CY2019Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.81
CY2019Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.59
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.68
CY2019Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.53
CY2019Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.77
CY2019Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.58
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.66
CY2019Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.51
CY2020	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	3
CY2020	ajg	Revenue From Contract With Customer Before Reimbursements Excluding Assessed Tax RevenueFromContractWithCustomerBeforeReimbursementsExcludingAssessedTax	6851900000
CY2020	ajg	Revenue From Contract With Customer Excluding Assessed Tax Reimbursements RevenueFromContractWithCustomerExcludingAssessedTaxReimbursements	151700000
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	7003600000
CY2020	us-gaap	Labor And Related Expense LaborAndRelatedExpense	3466500000
CY2020	us-gaap	Operating Expenses OperatingExpenses	906500000
CY2020	ajg	Cost Reimbursements CostReimbursements	151700000
CY2020	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	882100000
CY2020	us-gaap	Interest Expense InterestExpense	196400000
CY2020	us-gaap	Depreciation Depreciation	145100000
CY2020	us-gaap	Adjustment For Amortization AdjustmentForAmortization	417300000
CY2020	ajg	Change In Estimated Acquisition Earnout Payables ChangeInEstimatedAcquisitionEarnoutPayables	-32900000
CY2020	us-gaap	Costs And Expenses CostsAndExpenses	6132700000
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	870900000
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	12800000
CY2020	us-gaap	Profit Loss ProfitLoss	858100000
CY2020	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	39300000
CY2020	us-gaap	Net Income Loss NetIncomeLoss	818800000
CY2020	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	-2900000
CY2020	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	7003600000
CY2020Q4	us-gaap	Assets Assets	22331400000
CY2020Q4	us-gaap	Goodwill Goodwill	6127000000.0
CY2020Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	2399900000
CY2019	ajg	Revenue From Contract With Customer Before Reimbursements Excluding Assessed Tax RevenueFromContractWithCustomerBeforeReimbursementsExcludingAssessedTax	7056400000
CY2019	ajg	Revenue From Contract With Customer Excluding Assessed Tax Reimbursements RevenueFromContractWithCustomerExcludingAssessedTaxReimbursements	138600000
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	7195000000.0
CY2019	us-gaap	Labor And Related Expense LaborAndRelatedExpense	3339500000
CY2019	us-gaap	Operating Expenses OperatingExpenses	1068500000
CY2019	ajg	Cost Reimbursements CostReimbursements	138600000
CY2019	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	1352800000
CY2019	us-gaap	Interest Expense InterestExpense	179800000
CY2019	us-gaap	Depreciation Depreciation	140400000
CY2019	us-gaap	Adjustment For Amortization AdjustmentForAmortization	334000000.0
CY2019	ajg	Change In Estimated Acquisition Earnout Payables ChangeInEstimatedAcquisitionEarnoutPayables	15300000
CY2019	us-gaap	Costs And Expenses CostsAndExpenses	6568900000
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	626100000
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-89700000
CY2019	us-gaap	Profit Loss ProfitLoss	715800000
CY2019	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	47000000.0
CY2018	us-gaap	Adjustment For Amortization AdjustmentForAmortization	291200000
CY2018	ajg	Change In Estimated Acquisition Earnout Payables ChangeInEstimatedAcquisitionEarnoutPayables	9600000
CY2018	us-gaap	Costs And Expenses CostsAndExpenses	6454600000
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	479400000
CY2018	us-gaap	Operating Expenses OperatingExpenses	903700000
CY2018	ajg	Cost Reimbursements CostReimbursements	141600000
CY2018	us-gaap	Cost Of Goods And Services Sold CostOfGoodsAndServicesSold	1816000000.0
CY2018	us-gaap	Interest Expense InterestExpense	138400000
CY2018	us-gaap	Depreciation Depreciation	127800000
CY2019	us-gaap	Net Income Loss NetIncomeLoss	668800000
CY2019	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	-6700000
CY2019	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	7195000000.0
CY2019Q4	us-gaap	Assets Assets	19634800000
CY2019Q4	us-gaap	Goodwill Goodwill	5618500000
CY2019Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	2318700000
CY2018	ajg	Revenue From Contract With Customer Before Reimbursements Excluding Assessed Tax RevenueFromContractWithCustomerBeforeReimbursementsExcludingAssessedTax	6792400000
CY2018	ajg	Revenue From Contract With Customer Excluding Assessed Tax Reimbursements RevenueFromContractWithCustomerExcludingAssessedTaxReimbursements	141600000
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	6934000000.0
CY2018	us-gaap	Labor And Related Expense LaborAndRelatedExpense	3026300000
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	-196500000
CY2018	us-gaap	Profit Loss ProfitLoss	675900000
CY2018	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	42400000
CY2018	us-gaap	Net Income Loss NetIncomeLoss	633500000
CY2018	us-gaap	Foreign Currency Transaction Gain Loss Before Tax ForeignCurrencyTransactionGainLossBeforeTax	2900000
CY2018	us-gaap	Revenue From Contract With Customer Excluding Assessed Tax RevenueFromContractWithCustomerExcludingAssessedTax	6934000000.0
CY2018Q4	us-gaap	Assets Assets	16334000000.0
CY2018Q4	us-gaap	Goodwill Goodwill	4625600000
CY2018Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	1773000000.0

Files In Submission

Name	View Source	Status
0001564590-21-004555-index-headers.html	Edgar Link	pending
0001564590-21-004555-index.html	Edgar Link	pending
0001564590-21-004555.txt	Edgar Link	pending
0001564590-21-004555-xbrl.zip	Edgar Link	pending
ajg-10k_20201231.htm	Edgar Link	pending
ajg-10k_20201231_htm.xml	Edgar Link	completed
ajg-20201231.xsd	Edgar Link	pending
ajg-20201231_cal.xml	Edgar Link	unprocessable
ajg-20201231_def.xml	Edgar Link	unprocessable
ajg-20201231_lab.xml	Edgar Link	unprocessable
ajg-20201231_pre.xml	Edgar Link	unprocessable
ajg-ex1015_15.htm	Edgar Link	pending
ajg-ex211_173.htm	Edgar Link	pending
ajg-ex231_6.htm	Edgar Link	pending
ajg-ex241_12.htm	Edgar Link	pending
ajg-ex311_11.htm	Edgar Link	pending
ajg-ex312_9.htm	Edgar Link	pending
ajg-ex321_8.htm	Edgar Link	pending
ajg-ex322_10.htm	Edgar Link	pending
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
MetaLinks.json	Edgar Link	pending
R1.htm	Edgar Link	pending
R10.htm	Edgar Link	pending
R100.htm	Edgar Link	pending
R101.htm	Edgar Link	pending
R102.htm	Edgar Link	pending
R103.htm	Edgar Link	pending
R104.htm	Edgar Link	pending
R105.htm	Edgar Link	pending
R106.htm	Edgar Link	pending
R107.htm	Edgar Link	pending
R108.htm	Edgar Link	pending
R109.htm	Edgar Link	pending
R11.htm	Edgar Link	pending
R110.htm	Edgar Link	pending
R111.htm	Edgar Link	pending
R112.htm	Edgar Link	pending
R113.htm	Edgar Link	pending
R114.htm	Edgar Link	pending
R115.htm	Edgar Link	pending
R116.htm	Edgar Link	pending
R117.htm	Edgar Link	pending
R118.htm	Edgar Link	pending
R119.htm	Edgar Link	pending
R12.htm	Edgar Link	pending
R120.htm	Edgar Link	pending
R121.htm	Edgar Link	pending
R122.htm	Edgar Link	pending
R123.htm	Edgar Link	pending
R124.htm	Edgar Link	pending
R125.htm	Edgar Link	pending
R126.htm	Edgar Link	pending
R127.htm	Edgar Link	pending
R128.htm	Edgar Link	pending
R13.htm	Edgar Link	pending
R14.htm	Edgar Link	pending
R15.htm	Edgar Link	pending
R16.htm	Edgar Link	pending
R17.htm	Edgar Link	pending
R18.htm	Edgar Link	pending
R19.htm	Edgar Link	pending
R2.htm	Edgar Link	pending
R20.htm	Edgar Link	pending
R21.htm	Edgar Link	pending
R22.htm	Edgar Link	pending
R23.htm	Edgar Link	pending
R24.htm	Edgar Link	pending
R25.htm	Edgar Link	pending
R26.htm	Edgar Link	pending
R27.htm	Edgar Link	pending
R28.htm	Edgar Link	pending
R29.htm	Edgar Link	pending
R3.htm	Edgar Link	pending
R30.htm	Edgar Link	pending
R31.htm	Edgar Link	pending
R32.htm	Edgar Link	pending
R33.htm	Edgar Link	pending
R34.htm	Edgar Link	pending
R35.htm	Edgar Link	pending
R36.htm	Edgar Link	pending
R37.htm	Edgar Link	pending
R38.htm	Edgar Link	pending
R39.htm	Edgar Link	pending
R4.htm	Edgar Link	pending
R40.htm	Edgar Link	pending
R41.htm	Edgar Link	pending
R42.htm	Edgar Link	pending
R43.htm	Edgar Link	pending
R44.htm	Edgar Link	pending
R45.htm	Edgar Link	pending
R46.htm	Edgar Link	pending
R47.htm	Edgar Link	pending
R48.htm	Edgar Link	pending
R49.htm	Edgar Link	pending
R5.htm	Edgar Link	pending
R50.htm	Edgar Link	pending
R51.htm	Edgar Link	pending
R52.htm	Edgar Link	pending
R53.htm	Edgar Link	pending
R54.htm	Edgar Link	pending
R55.htm	Edgar Link	pending
R56.htm	Edgar Link	pending
R57.htm	Edgar Link	pending
R58.htm	Edgar Link	pending
R59.htm	Edgar Link	pending
R6.htm	Edgar Link	pending
R60.htm	Edgar Link	pending
R61.htm	Edgar Link	pending
R62.htm	Edgar Link	pending
R63.htm	Edgar Link	pending
R64.htm	Edgar Link	pending
R65.htm	Edgar Link	pending
R66.htm	Edgar Link	pending
R67.htm	Edgar Link	pending
R68.htm	Edgar Link	pending
R69.htm	Edgar Link	pending
R7.htm	Edgar Link	pending
R70.htm	Edgar Link	pending
R71.htm	Edgar Link	pending
R72.htm	Edgar Link	pending
R73.htm	Edgar Link	pending
R74.htm	Edgar Link	pending
R75.htm	Edgar Link	pending
R76.htm	Edgar Link	pending
R77.htm	Edgar Link	pending
R78.htm	Edgar Link	pending
R79.htm	Edgar Link	pending
R8.htm	Edgar Link	pending
R80.htm	Edgar Link	pending
R81.htm	Edgar Link	pending
R82.htm	Edgar Link	pending
R83.htm	Edgar Link	pending
R84.htm	Edgar Link	pending
R85.htm	Edgar Link	pending
R86.htm	Edgar Link	pending
R87.htm	Edgar Link	pending
R88.htm	Edgar Link	pending
R89.htm	Edgar Link	pending
R9.htm	Edgar Link	pending
R90.htm	Edgar Link	pending
R91.htm	Edgar Link	pending
R92.htm	Edgar Link	pending
R93.htm	Edgar Link	pending
R94.htm	Edgar Link	pending
R95.htm	Edgar Link	pending
R96.htm	Edgar Link	pending
R97.htm	Edgar Link	pending
R98.htm	Edgar Link	pending
R99.htm	Edgar Link	pending
report.css	Edgar Link	pending
Show.js	Edgar Link	pending

Create your account

Find Stocks Worth Researching

Deeply Understand Businesses

Value Businesses Intelligently

$AJG
Arthur J. Gallagher & Co. Stock $ajg

2020 Q4 Form 10-K Financial Statement

#000156459021004555 Filed on February 08, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$AJG Arthur J. Gallagher & Co. Stock $ajg

2020 Q4 Form 10-K Financial Statement

#000156459021004555 Filed on February 08, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$AJG
Arthur J. Gallagher & Co. Stock $ajg