XML 95 R82.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Deferred Compensation - Additional Information (Detail) - USD ($) shares in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2020 | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Mar. 31, 2018 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Investments And Employee Deferred Compensation Plan [Line Items] |  |  |  |  |  |  |  |
Deferred Equity Participation Plan, distributions to key executives, age |  |  |  |  |  | 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. |  |
Deferred Equity Participation Sub-plans, distributions requisite service description |  |  |  |  |  | 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. |  |
Deferred Equity Participation Sub-plans, distributions to key executives, age |  |  |  |  |  | age 65 |  |
Deferred Equity Participation Plan (DEPP) [Member] |  |  |  |  |  |  |  |
Investments And Employee Deferred Compensation Plan [Line Items] |  |  |  |  |  |  |  |
Awards approved by committee, value | $ 17,000,000.0 |  |  | $ 14,100,000 | $ 10,100,000 |  |  |
Charge to compensation expenses related to awards |  |  |  |  |  | $ 14,100,000 | $ 12,200,000 | $ 9,800,000
Unearned deferred compensation, value |  |  |  |  |  | $ 67,400,000 | $ 60,500,000 |
Unearned deferred compensation, shares |  |  |  |  |  | 2.7 | 2.6 |
Total intrinsic value of unvested equity based awards |  |  |  |  |  | $ 451,000,000.0 | $ 327,800,000 |
Cash and equity awards with aggregate fair value vested and distributed to participants |  |  |  |  |  | 19,100,000 | 41,200,000 | 3,100,000
Deferred Equity Participation Plan Sub Plans [Member] |  |  |  |  |  |  |  |
Investments And Employee Deferred Compensation Plan [Line Items] |  |  |  |  |  |  |  |
Awards approved by committee, value |  |  |  |  |  | 3,200,000 | 1,800,000 | 2,600,000
Charge to compensation expenses related to awards |  |  |  |  |  | 2,300,000 | 1,900,000 | 2,400,000
Distributions from the sub-plans |  |  |  |  |  | 0 | 0 | 500,000
Deferred Cash Participation Plan (DCPP) [Member] |  |  |  |  |  |  |  |
Investments And Employee Deferred Compensation Plan [Line Items] |  |  |  |  |  |  |  |
Awards approved by committee, value | $ 3,000,000.0 | $ 1,600,000 | $ 7,700,000 | $ 2,400,000 |  | 7,200,000 |  |
Charge to compensation expenses related to awards |  |  |  |  |  | 9,600,000 | 6,900,000 | 5,200,000
Cash and equity awards with aggregate fair value vested and distributed to participants |  |  |  |  |  | $ 6,700,000 | $ 3,200,000 | $ 2,500,000

X
- Definition Cash and equity award with aggregate fair value vested and distributed to participants. + References No definition available. + Details
Name: | ajg_CashAndEquityAwardWithAggregateFairValueVestedAndDistributedToParticipants
Namespace Prefix: | ajg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Compensation approved by committee, value + References No definition available. + Details
Name: | ajg_CompensationApprovedByCommitteeValue
Namespace Prefix: | ajg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Deferred Equity Participation Plan, Distributions to Key Executives, Age + References No definition available. + Details
Name: | ajg_DeferredEquityParticipationPlanDistributionsToKeyExecutivesAge
Namespace Prefix: | ajg_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Deferred equity participation sub plan distributions requisite service description. + References No definition available. + Details
Name: | ajg_DeferredEquityParticipationSubPlanDistributionsRequisiteServiceDescription
Namespace Prefix: | ajg_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Deferred equity participation sub plan distributions to key executives age. + References No definition available. + Details
Name: | ajg_DeferredEquityParticipationSubPlanDistributionsToKeyExecutivesAge
Namespace Prefix: | ajg_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Investments And Employee Deferred Compensation Plan [Line Items] + References No definition available. + Details
Name: | ajg_InvestmentsAndEmployeeDeferredCompensationPlanLineItems
Namespace Prefix: | ajg_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Proceeds From Sub Plan + References No definition available. + Details
Name: | ajg_ProceedsFromSubPlan
Namespace Prefix: | ajg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Unearned Deferred Compensation, Shares + References No definition available. + Details
Name: | ajg_UnearnedDeferredCompensationShare
Namespace Prefix: | ajg_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Unearned Deferred Compensation, Value + References No definition available. + Details
Name: | ajg_UnearnedDeferredCompensationValue
Namespace Prefix: | ajg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of expense for award under share-based payment arrangement. Excludes amount capitalized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5047-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=122041274&loc=d3e301413-122809 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_AllocatedShareBasedCompensationExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_AwardTypeAxis=ajg_DeferredEquityParticipationPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=ajg_DeferredEquityParticipationPlanSubPlansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=ajg_DeferredCashParticipationPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |