XML 55 R44.htm IDEA: XBRL DOCUMENT v3.25.3

Contracts with Customers - Summary of Changes in Deferred Revenue Balances (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2025 USD ($)
Change in Contract with Customer, Liability [Roll Forward]
Deferred revenue beginning balance	$ 604.3
Incremental deferred revenue	434.8
Revenue recognized during the nine-month period ended September 30, 2025 included in deferred revenue at December 31, 2024	(403.1)
Net change in collected billings/deposits received from customers	7.4
Impact of change in foreign exchange rates	27.3
Deferred revenue recognized from business acquisitions	220.4
Deferred revenue ending balance	891.1
Brokerage
Change in Contract with Customer, Liability [Roll Forward]
Deferred revenue beginning balance	430.9
Incremental deferred revenue	351.9
Revenue recognized during the nine-month period ended September 30, 2025 included in deferred revenue at December 31, 2024	(328.8)
Net change in collected billings/deposits received from customers	9.1
Impact of change in foreign exchange rates	26.4
Deferred revenue recognized from business acquisitions	220.4
Deferred revenue ending balance	709.9
Risk Management
Change in Contract with Customer, Liability [Roll Forward]
Deferred revenue beginning balance	173.4
Incremental deferred revenue	82.9
Revenue recognized during the nine-month period ended September 30, 2025 included in deferred revenue at December 31, 2024	(74.3)
Net change in collected billings/deposits received from customers	(1.7)
Impact of change in foreign exchange rates	0.9
Deferred revenue recognized from business acquisitions	0.0
Deferred revenue ending balance	$ 181.2

X

- Definition

Change in Contract with Customer, Liability

+ References

No definition available.

+ Details

Name:	ajg_ChangeInContractWithCustomerLiabilityRollForward
Namespace Prefix:	ajg_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Contract with customer impact of change in foreign exchange rates.

+ References

No definition available.

+ Details

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

X

- Definition

Contract with customer, liability, additions.

+ References

No definition available.

+ Details

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

X

- Definition

Net change in collected billings and deposits received from customers.

+ References

No definition available.

+ Details

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

X

- Definition

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479837/606-10-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-8

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479837/606-10-45-2

+ Details

Name:	us-gaap_ContractWithCustomerLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Amount of increase (decrease) in obligation to transfer good or service to customer for which consideration from customer has been received or is due, from business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-10

+ Details

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

X

- Definition

Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-8

+ Details

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

X

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=ajg_BrokerageSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=ajg_RiskManagementSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: