XML 80 R69.htm IDEA: XBRL DOCUMENT v3.20.2

Derivatives and Hedging Activity - Summary of Amounts of Derivative Gains (Losses) Recognized In Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Loss	[1]	$ 8.1	$ (29.4)	$ (125.4)	$ (46.6)
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Income Loss into Earnings		(1.3)	(1.2)	(2.5)	(1.9)
Amount of Gain (Loss) Recognized in Earnings Related to Amount Excluded from Effectiveness Testing		0.5	0.4	0.7	0.8
Interest expense [Member] | Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Loss	[1]	6.1	(25.8)	(108.1)	(46.7)
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Income Loss into Earnings		(0.3)	(0.3)	(0.6)	(0.6)
Commission revenue [Member] | Foreign Exchange Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Accumulated Other Comprehensive Loss	[1]	2.0	(3.6)	(17.3)	0.1
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Income Loss into Earnings		(0.1)	(0.1)	(0.5)	(0.2)
Amount of Gain (Loss) Recognized in Earnings Related to Amount Excluded from Effectiveness Testing		(0.1)	(0.2)	(0.3)	(0.4)
Compensation expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Income Loss into Earnings		(0.5)	(0.4)	(0.8)	(0.6)
Amount of Gain (Loss) Recognized in Earnings Related to Amount Excluded from Effectiveness Testing		0.4	0.3	0.6	0.7
Operating expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Income Loss into Earnings		(0.4)	(0.4)	(0.6)	(0.5)
Amount of Gain (Loss) Recognized in Earnings Related to Amount Excluded from Effectiveness Testing		$ 0.2	$ 0.3	$ 0.4	$ 0.5
[1] For the three-month and six-month periods ended June 30, 2020, the amount excluded from the assessment of hedge effectiveness for our foreign exchange contracts recognized in accumulated other comprehensive loss was a loss of $0.1 million and $0.4 million, respectively.

X

- Definition

The Amount of Gain Loss Recognized Effectiveness Testing

+ References

No definition available.

+ Details

Name:	ajg_AmountOfGainLossRecognizedEffectivenessTesting
Namespace Prefix:	ajg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeInstrumentsGainLossLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4D
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624177-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624171-113959

+ Details

Name:	us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Amount, before tax and after reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669646-108580

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=121641772&loc=d3e637-108580

+ Details

Name:	us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_InterestExpenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_IncomeStatementLocationAxis=ajg_CommissionRevenueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_IncomeStatementLocationAxis=ajg_CompensationExpenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_OperatingExpenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: