XML 69 R58.htm IDEA: XBRL DOCUMENT
v3.21.1

Unpaid losses and loss expenses Unpaid losses and loss expenses (Narrative) (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2021 | Mar. 31, 2020
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | $ (192) | $ (118)
Long Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | (37) | (32)
Short Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | (155) | (86)
North America Commercial P&C Insurance [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | (127) | (105)
North America Commercial P&C Insurance [Member] | Long Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | (46) | (43)
North America Commercial P&C Insurance [Member] | Short Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | (81) | (62)
North America Commercial P&C Insurance [Member] | Professional Malpractice Liability Insurance [Member] | Long Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | (51) |
North America Commercial P&C Insurance [Member] | Environmental lines [Member] | Long Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | (35) |
North America Commercial P&C Insurance [Member] | Commercial Excess and Umbrella [Member] | Long Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | 57 | 49
North America Commercial P&C Insurance [Member] | General Liability [Member] | Long Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development |  | 23
North America Commercial P&C Insurance [Member] | Accident years 2016 and prior [Member] | Professional Malpractice Liability Insurance [Member] | Long Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development |  | (66)
North America Commercial P&C Insurance [Member] | Accident years 2016 and prior [Member] | Environmental lines [Member] | Long Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development |  | (43)
North America Commercial P&C Insurance [Member] | Accident years 2016 and prior [Member] | Workers' Compensation Insurance [Member] | Long Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development |  | (28)
North America Commercial P&C Insurance [Member] | Short-duration Insurance Contracts, Accident Year 2018 [Member] | Surety Product Line [Member] | Short Tail [Member] | Catastrophe [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development |  | (31)
North America Commercial P&C Insurance [Member] | Accident years 2018 - 2019 [Member] | Surety Product Line [Member] | Short Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | (49) |
North America Commercial P&C Insurance [Member] | Accident years 2018 - 2019 [Member] | Accident and Health Insurance Product Line [Member] | Short Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development |  | (36)
North America Commercial P&C Insurance [Member] | Short-Duration Insurance Contract, Accident Year 2020 | Property and Inland Marine [Member] | Short Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | (25) |
North America Commercial P&C Insurance [Member] | Accident Years 2019 - 2020 | Professional Malpractice Liability Insurance [Member] | Short Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | 41 |
North America Commercial P&C Insurance [Member] | Accident Years 2019 - 2020 | Accident and Health Insurance Product Line [Member] | Short Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | (48) |
North America Agricultural Insurance [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | (2) | (14)
North America Agricultural Insurance [Member] | Long Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | 0 | 0
North America Agricultural Insurance [Member] | Short Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | (2) | (14)
Corporate Segment [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | 9 | 11
Corporate Segment [Member] | Long Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | 9 | 11
Corporate Segment [Member] | Short Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | 0 | 0
Overseas General Insurance [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | (25) | (4)
Overseas General Insurance [Member] | Long Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | 0 | 0
Overseas General Insurance [Member] | Short Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | (25) | (4)
North America Personal P&C Insurance [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development |  | 1
North America Personal P&C Insurance [Member] | Long Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | 0 | 0
North America Personal P&C Insurance [Member] | Short Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | (40) | 1
North America Personal P&C Insurance [Member] | Short-Duration Insurance Contract, Accident Year 2020 |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | (40) |
Global Reinsurance [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | (7) | (7)
Global Reinsurance [Member] | Long Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | 0 | 0
Global Reinsurance [Member] | Short Tail [Member] |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |
Net Prior Period Development | $ (7) | $ (7)

X
- Definition Net Prior Period Development - Amount, after effects of reinstatement premiums, expense adjustments, and net premiums earned adjustments for claims incurred in prior reporting periods and related claims settlement costs. + References No definition available. + Details
Name: | cb_NetPriorPeriodDevelopment
Namespace Prefix: | cb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsClaimDurationAxis=cb_LongTailMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsClaimDurationAxis=cb_ShortTailMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=cb_SegmentNorthAmericaCommercialPCInsuranceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=us-gaap_ProfessionalMalpracticeLiabilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=cb_EnvironmentallinesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=cb_CommercialExcessandUmbrellaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=us-gaap_GeneralLiabilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=cb_Accidentyears2016andpriorMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=us-gaap_WorkersCompensationInsuranceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractsAccidentYear2018Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=us-gaap_SuretySegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis=us-gaap_CatastropheMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=cb_Accidentyears20182019Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=us-gaap_AccidentAndHealthInsuranceSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractAccidentYear2020Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=cb_PropertyAndInlandMarineMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=cb_AccidentYears20192020Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=cb_SegmentInsuranceNorthAmericanAgricultureMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=us-gaap_CorporateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=cb_SegmentInsuranceOverseasGeneralMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=cb_NorthAmericaPersonalPCInsuranceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=cb_SegmentGlobalReinsuranceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |