XML 76 R64.htm IDEA: XBRL DOCUMENT v3.8.0.1

Derivatives and Hedging Activity - Summary of Amounts of Derivative Gains (Losses) Recognized In Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses) recognized in accumulated other comprehensive loss	$ 10.2	$ (19.4)
Derivative gains (losses) reclassified from accumulated other comprehensive loss into income (effective portion)	(5.7)	(5.2)
Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses) recognized in accumulated other comprehensive loss	(1.6)	(3.3)
Foreign Exchange Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses) recognized in accumulated other comprehensive loss	11.8	(16.1)
Derivative gains (losses) reclassified from accumulated other comprehensive loss into income (effective portion)	(5.7)	(5.2)
Commission Revenue [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses) recognized in accumulated other comprehensive loss	7.9	(17.3)
Derivative gains (losses) reclassified from accumulated other comprehensive loss into income (effective portion)	(7.6)	(5.7)
Commission Revenue [Member] | Foreign Exchange Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses) recognized in accumulated other comprehensive loss	7.9	(17.3)
Derivative gains (losses) reclassified from accumulated other comprehensive loss into income (effective portion)	(7.6)	(5.7)
Compensation Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses) recognized in accumulated other comprehensive loss	2.3	0.7
Derivative gains (losses) reclassified from accumulated other comprehensive loss into income (effective portion)	1.1	0.3
Compensation Expense [Member] | Foreign Exchange Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses) recognized in accumulated other comprehensive loss	2.3	0.7
Derivative gains (losses) reclassified from accumulated other comprehensive loss into income (effective portion)	1.1	0.3
Operating Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses) recognized in accumulated other comprehensive loss	1.6	0.5
Derivative gains (losses) reclassified from accumulated other comprehensive loss into income (effective portion)	0.8	0.2
Operating Expense [Member] | Foreign Exchange Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses) recognized in accumulated other comprehensive loss	1.6	0.5
Derivative gains (losses) reclassified from accumulated other comprehensive loss into income (effective portion)	0.8	0.2
Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses) recognized in accumulated other comprehensive loss	(1.6)	(3.3)
Interest Expense [Member] | Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses) recognized in accumulated other comprehensive loss	$ (1.6)	$ (3.3)

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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4D
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624177-113959

+ Details

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

X

- Definition

The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

+ Details

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

X

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateContractMember
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_CommissionRevenueMember
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:

X

- Details

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