XML 98 R81.htm IDEA: XBRL DOCUMENT
v3.20.4

Investment Information - Other Investments (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Schedule Of Other Investments [Line Items] |  |
Other investments and fair value option investments | $ 2,331,885 | $ 2,429,316
Fair value option | Term loan investments |  |
Schedule Of Other Investments [Line Items] |  |
Other investments and fair value option investments | 1,231,731 | 1,326,018
Fair value option | Lending |  |
Schedule Of Other Investments [Line Items] |  |
Other investments and fair value option investments | 572,636 | 602,841
Fair value option | Credit related funds |  |
Schedule Of Other Investments [Line Items] |  |
Other investments and fair value option investments | 90,780 | 123,020
Fair value option | Energy |  |
Schedule Of Other Investments [Line Items] |  |
Other investments and fair value option investments | 65,813 | 97,402
Fair value option | Investment grade fixed income |  |
Schedule Of Other Investments [Line Items] |  |
Other investments and fair value option investments | 138,646 | 151,594
Fair value option | Infrastructure |  |
Schedule Of Other Investments [Line Items] |  |
Other investments and fair value option investments | 165,516 | 61,786
Fair value option | Private equity |  |
Schedule Of Other Investments [Line Items] |  |
Other investments and fair value option investments | 48,750 | 49,376
Fair value option | Real estate |  |
Schedule Of Other Investments [Line Items] |  |
Other investments and fair value option investments | $ 18,013 | $ 17,279

X
- Definition Other investments and fair value option investments. + References No definition available. + Details
Name: | acgl_OtherInvestmentsAndOtherFairValueOptionInvestments
Namespace Prefix: | acgl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition -- None. No documentation exists for this element. -- + References No definition available. + Details
Name: | acgl_ScheduleOfOtherInvestmentsLineItems
Namespace Prefix: | acgl_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_InvestmentTypeAxis=acgl_FairValueOptionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentSecondaryCategorizationAxis=acgl_TermLoanInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentSecondaryCategorizationAxis=acgl_OtherInvestmentsLendingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentSecondaryCategorizationAxis=acgl_CreditRelatedFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentSecondaryCategorizationAxis=acgl_OtherInvestmentsEnergyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentSecondaryCategorizationAxis=acgl_InvestmentGradeFixedIncomeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentSecondaryCategorizationAxis=acgl_OtherInvestmentsInfrastructureMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentSecondaryCategorizationAxis=us-gaap_PrivateEquityFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentSecondaryCategorizationAxis=us-gaap_RealEstateFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |