XML 88 R73.htm IDEA: XBRL DOCUMENT
v3.20.4

Credit and Other Debt Agreements - Summary of Corporate and Other Debt (Detail) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | $ 4,551.6 | $ 4,613.6
Less unamortized debt acquisition costs on Note Purchase Agreements | (7.0) | (6.9)
Semi-annual payments of interest, Net | 4,544.6 | 4,606.7
Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 4,348.0 | 3,923.0
Fixed Rate of 3.48%, Balloon Due June 24, 2020 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest |  | 50.0
Fixed Rate of 3.99%, Balloon Due July 10, 2020 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest |  | 50.0
Fixed Rate of 5.18%, Balloon Due February 10, 2021 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 75.0 | 75.0
Fixed Rate of 3.69%, Balloon Due June 14, 2022 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 200.0 | 200.0
Fixed Rate of 5.49%, Balloon Due February 10, 2023 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 50.0 | 50.0
Fixed Rate of 4.13%, Balloon Due June 24, 2023 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 200.0 | 200.0
Floating Rate of 1.65% LIBOR Plus Balloon Due August 2, 2023 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest |  | 50.0
Fixed Rate of 4.72%, Balloon due February 13, 2024 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 100.0 | 100.0
Fixed Rate of 4.58%, Balloon Due February 27, 2024 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 325.0 | 325.0
Floating Interest Rate of 1.40% LIBOR Plus Balloon Due June 13, 2024 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 50.0 | 50.0
Fixed Rate of 4.31%, Balloon Due June 24, 2025 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 200.0 | 200.0
Fixed Rate of 4.85%, Balloon due February 13, 2026 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 140.0 | 140.0
Fixed Rate of 4.73%, Balloon Due February 27, 2026 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 175.0 | 175.0
Fixed Rate of 4.40%, Balloon Due June 2, 2026 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 175.0 | 175.0
Fixed Rate of 4.36%, Balloon Due June 24, 2026 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 150.0 | 150.0
Fixed Rate of 3.75%, Balloon Due January 30, 2027 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 30.0 |
Fixed Rate of 4.09%, Balloon Due June 27, 2027 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 125.0 | 125.0
Fixed Rate of 4.09%, Balloon Due August 2, 2027 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 125.0 | 125.0
Fixed Rate of 4.14%, Balloon Due August 4, 2027 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 98.0 | 98.0
Fixed Rate of 3.46%, Balloon Due December 1, 2027 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 100.0 | 100.0
Fixed Rate of 4.55%, Balloon Due June 2, 2028 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 75.0 | 75.0
Fixed Rate of 4.34%, Balloon due June 13, 2028 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 125.0 | 125.0
Fixed Rate of 5.04%, Balloon due February 13, 2029 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 100.0 | 100.0
Fixed Rate of 4.98%, Balloon Due February 27, 2029 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 100.0 | 100.0
Fixed Rate of 4.19%, Balloon Due June 27, 2029 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 50.0 | 50.0
Fixed Rate of 4.19%, Balloon Due August 2, 2029 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 50.0 | 50.0
Fixed Rate of 3.48%, Balloon Due December 2, 2029 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 50.0 | 50.0
Fixed Rate of 3.99%, Balloon Due January 30, 2030 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 341.0 |
Fixed Rate of 4.44%, Balloon Due June 13, 2030 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 125.0 | 125.0
Fixed Rate of 5.14%, Balloon due March 13, 2031 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 180.0 | 180.0
Fixed Rate of 4.70%, Balloon Due June 2, 2031 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 25.0 | 25.0
Fixed Rate of 4.09%, Balloon Due January 30, 2032 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 69.0 |
Fixed Rate of 4.34%, Balloon Due June 27, 2032 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 75.0 | 75.0
Fixed Rate of 4.34%, Balloon Due August 2, 2032 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 75.0 | 75.0
Fixed Rate of 4.59%, Balloon due June 13, 2033 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 125.0 | 125.0
Fixed Rate of 5.29%, balloon due March 13, 2034 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 40.0 | 40.0
Fixed Rate of 4.48%, Balloon Due June 12, 2034 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 175.0 | 175.0
Fixed Rate of 4.24%, Balloon Due January 30, 2035 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 79.0 |
Fixed Rate of 4.69%, Balloon Due June 13, 2038 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 75.0 | 75.0
Fixed Rate of 5.45%, balloon due March 13, 2039 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 40.0 | 40.0
Fixed Rate of 4.49%, Balloon Due January 30, 2040 [Member] | Note Purchase Agreements [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 56.0 |
Prime or LIBOR Plus up to 1.45%, Expires June 7, 2024 [Member] | Multi Currency Credit Agreement [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest |  | 520.0
Interbank Rates Plus 1.400% Expires September 15, 2022 [Member] | AUD Denominated Tranche [Member] | Facility B [Member] | Premium Financing Debt Facility [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 193.1 | 142.1
Interbank Rates Plus 0.730% Expires September 15, 2022 [Member] | AUD Denominated Tranche [Member] | Facility C and D [Member] | Premium Financing Debt Facility [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest |  | 18.8
Interbank Rates Plus 0.940% Expires September 15, 2022 [Member] | NZD Denominated Tranche [Member] | Facility C and D [Member] | Premium Financing Debt Facility [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | 10.5 | 9.7
Interbank Rates Expires September 15, 2022 [Member] | Premium Financing Debt Facility [Member] |  |
Debt Instrument [Line Items] |  |
Semi-annual payments of interest | $ 203.6 | $ 170.6

X
- Definition Debt long-term and short-term combined amount gross. + References No definition available. + Details
Name: | ajg_DebtLongTermAndShortTermCombinedAmountGross
Namespace Prefix: | ajg_
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_DebtInstrumentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the aggregate of total long-term debt, including current maturities and short-term debt. + References No definition available. + Details
Name: | us-gaap_DebtLongtermAndShorttermCombinedAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.17) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_UnamortizedDebtIssuanceExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_LineOfCreditFacilityAxis=ajg_NotePurchaseAgreementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfThreePointFourEightPercentBalloonDueJuneTwentyFourTwoThousandTwentyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfThreePointNineNinePercentBalloonDueJulyTenTwoThousandTwentyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFivePointOneEightPercentBalloonDueFebruaryTenTwoThousandTwentyOneMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfThreePointSixNinePercentBalloonDueJuneFourteenTwoThousandTwentyTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFivePointFourNinePercentBalloonDueFebruaryTenTwoThousandTwentyThreeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointOneThreePercentageBalloonDueJuneTwentyFourTwoThousandTwentyThreeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FloatingInterestRateOfOnePointOneSixFivePercentLIBORPlusBalloonDueAugustTwoTwoThousandTwentyThreeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointSevenTwoPercentBalloonDueFebruaryThirteenTwoThousandTwentyFourMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointFiveEightPercentBalloonDueFebruaryTwentySevenTwoThousandTwentyFourMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FloatingInterestRateOfOnePointFourZeroPercentLIBORPlusBalloonDueJuneThirteenTwoThousandTwentyFourMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointThreeOnePercentBalloonDueJuneTwentyFourTwoThousandTwentyFiveMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointEightFivePercentBalloonDueFebruaryThirteenTwoThousandTwentySixMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointSevenThreePercentBalloonDueFebruaryTwentySevenTwoThousandTwentySixMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointFourZeroPercentBalloonDueJuneTwoTwoThousandTwentySixMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointThreeSixPercentBalloonDueJuneTwentyFourTwoThousandTwentySixMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfThreePointSevenFivePercentBalloonDueJanuaryThirtyTwoThousandTwentySevenMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointZeroNinePercentBalloonDueJuneTwentySevenTwoThousandTwentySevenMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointZeroNinePercentBalloonDueAugustTwoTwoThousandTwentySevenMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointOneFourPercentBalloonDueAugustFourTwoThousandTwentySevenMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfThreePointFourSixPercentageBalloonDueDecemberOneTwoThousandTwentySevenMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointFiveFivePercentBalloonDueJuneTwoTwoThousandTwentyEightMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointThreeFourPercentBalloonDueJuneThirteenTwoThousandTwentyEightMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFivePointZeroFourPercentageBalloonDueFebruaryThirteenTwoThousandTwentyNineMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointNineEightPercentBalloonDueFebruaryTwentySevenTwoThousandTwentyNineMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointOneNinePercentBalloonDueJuneTwentySevenTwoThousandTwentyNineMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointOneNinePercentBalloonDueAugustTwoTwoThousandTwentyNineMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfThreePointFourEightPercentBalloonDueDecemberTwoTwothousandTwentyNineMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfThreePointNineNinePercentBalloonDueJanuaryThirtyTwoThousandThirtyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointFourFourPercentBalloonDueJuneThirteenTwoThousandThirtyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFivePointOneFourPercentBalloonDueMarchThirteenTwoThousandThirtyOneMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointSevenZeroPercentBalloonDueJuneTwoTwoThousandThirtyOneMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointZeroNinePercentBalloonDueJanuaryThirtyTwoThousandThirtyTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointThreeFourPercentBalloonDueJuneTwentySevenTwoThousandThirtyTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointThreeFourPercentBalloonDueAugustTwoTwoThousandThirtyTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointFiveNinePercentBalloonDueJuneThirteenTwoThousandThirtyThreeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFivePointTwoNinePercentBalloonDueMarchThirteenTwoThousandThirtyFourMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointFourEightPercentBalloonDueJuneTwelveTwoThousandThirtyFourMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointTwoFourPercentBalloonDueJanuaryThirtyTwoThousandThirtyFiveMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointSixNinePercentBalloonDueJuneThirteenTwoThousandThirtyEightMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFivePointFourFivePercentBalloonDueMarchThirteenTwoThousandThirtyNineMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_FixedRateOfFourPointFourNinePercentBalloonDueJanuaryThirtyTwoThousandFortyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_PrimeOrLiborPlusUpToOnePointFourFivePercentExpiresJuneSevenTwoThousandTwentyFourMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LineOfCreditFacilityAxis=ajg_UnsecuredMulticurrencyCreditAgreementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_InterbankRatePlusOnePointFourZeroZeroPercentExpiresSeptemberFifteenTwoThousandTwentyTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LineOfCreditFacilityAxis=ajg_AudDenominatedTrancheMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ajg_FacilityBMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=ajg_PremiumFinancingDebtFacilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_InterbankRatePlusZeroPointSevenThreeZeroPercentExpiresSeptemberFifteenTwoThousandTwentyTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=ajg_FacilityCAndFacilityDMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_InterbankRatePlusZeroPointNineFourZeroPercentExpiresSeptemberFifteenTwoThousandTwentyTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LineOfCreditFacilityAxis=ajg_NzdDenominatedTrancheMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ExtinguishmentOfDebtAxis=ajg_InterbankRatesExpiresSeptemberFifteenTwoThousandTwentyTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |