XML 62 R49.htm IDEA: XBRL DOCUMENT v3.20.2

Contracts with Customers - Summary of Expected Revenue Related to Performance Obligations (Detail) $ in Millions	Sep. 30, 2020 USD ($)
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 531.4
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 310.5
Remaining performance obligation, expected timing of satisfaction, period	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 147.1
Remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 43.4
Remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2023-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 13.0
Remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2024-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 6.3
Remaining performance obligation, expected timing of satisfaction, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2025-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 11.1
Remaining performance obligation, expected timing of satisfaction, period
Brokerage [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 345.4
Brokerage [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 230.8
Remaining performance obligation, expected timing of satisfaction, period	3 months
Brokerage [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 95.6
Remaining performance obligation, expected timing of satisfaction, period	1 year
Brokerage [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 16.9
Remaining performance obligation, expected timing of satisfaction, period	1 year
Brokerage [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2023-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 1.1
Remaining performance obligation, expected timing of satisfaction, period	1 year
Brokerage [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2024-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 0.5
Remaining performance obligation, expected timing of satisfaction, period	1 year
Brokerage [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2025-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 0.5
Remaining performance obligation, expected timing of satisfaction, period
Risk Management [Member]
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 186.0
Risk Management [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 79.7
Remaining performance obligation, expected timing of satisfaction, period	3 months
Risk Management [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 51.5
Remaining performance obligation, expected timing of satisfaction, period	1 year
Risk Management [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 26.5
Remaining performance obligation, expected timing of satisfaction, period	1 year
Risk Management [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2023-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 11.9
Remaining performance obligation, expected timing of satisfaction, period	1 year
Risk Management [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2024-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 5.8
Remaining performance obligation, expected timing of satisfaction, period	1 year
Risk Management [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2025-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Expected revenue related to performance obligations	$ 10.6
Remaining performance obligation, expected timing of satisfaction, period

X

- Definition

Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130556-203045

+ Details

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

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

X

- Definition

Period in which remaining performance obligation is expected to be recognized as revenue, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130556-203045

+ Details

Name:	us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

X

- Details

Name:	us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis=2020-10-01
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis=2021-01-01
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis=2022-01-01
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis=2023-01-01
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis=2024-01-01
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis=2025-01-01
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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: