XML 68 R53.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Summary of significant accounting policies (Narrative) (Detail) - USD ($) $ in Millions |  |  | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | ---
Dec. 31, 2017 | Jan. 14, 2016 | Dec. 31, 2017 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Jan. 01, 2019 | Dec. 31, 2015
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Deposit assets reflected in Other assets | $ 89 |  |  | $ 89 |  | $ 97 |  | $ 89 |  |  |  |
Unpaid losses and loss expenses | 63,179 |  |  | 63,179 |  | 62,960 |  | 63,179 |  | $ 60,540 |  | $ 37,303
Deposit liabilities included in Deposit liabilities | 100 |  |  | 100 |  | 97 |  | 100 |  |  |  |
Borrowings under Guaranteed Investment Agreements | 1,800 |  |  | 1,800 |  |  |  | 1,800 |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Deferred Policy Acquisition Costs, Amortization Expense |  |  |  |  |  | 5,912 |  | 5,781 |  | 5,904 |  |
Deferred Advertising Costs | 271 |  |  | 271 |  | $ 255 |  | 271 |  |  |  |
Deferred Marketing Costs, Amortization Period |  |  |  |  |  | 10 years |  |  |  |  |  |
Recoverable from unrated reinsurers, ceded reserve, default factor (percent) |  |  |  |  |  | 34.00% |  |  |  |  |  |
Reinsurance business assumed |  |  |  |  |  | $ 14 |  | 18 |  |  |  |
Percentage of fair value of loaned securities |  |  |  |  |  | 102.00% |  |  |  |  |  |
Quality assessment threshold used in goodwill impairment testing |  |  |  |  |  | 50.00% |  |  |  |  |  |
Affiliated notional cash pooling program | 0 | [1] |  | 0 | [1] | $ 0 | [2] | 0 | [1] |  |  |
Net operating results of ESIS included within Administrative expenses |  |  |  |  |  | $ 49 |  | 38 |  | 32 |  |
Income Tax Examination, Description |  |  |  |  |  | 0.5 |  |  |  |  |  |
Property, Plant and Equipment, Net | 1,300 |  |  | 1,300 |  | $ 1,700 |  | 1,300 |  |  |  |
Chubb integration expenses |  |  |  |  |  | $ 59 |  | $ 310 |  | 492 |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount |  |  |  | 475 |  |  |  |  |  |  |  |
Tax Year 2018 [Member] |  |  |  |  |  |  |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent |  |  |  |  |  | 21.00% |  |  |  |  |  |
Tax Year 2017 [Member] |  |  |  |  |  |  |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent |  |  |  |  |  | 35.00% |  | 35.00% |  |  |  |
The Chubb Corporation [Member] | Debt Securities [Member] |  |  |  |  |  |  |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Assets, Fair Value Adjustment |  |  | $ 1,652 |  |  | $ 520 |  |  |  |  |  |
Adjustments for New Accounting Pronouncement [Member] |  |  |  |  |  |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Effect on Retained Earnings, Tax | 7 |  |  |  |  |  |  |  |  |  |  |
Accounting Standards Update 2017-08 [Member] |  |  |  |  |  |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Effect on Retained Earnings, before Tax |  |  |  |  |  | 15 |  |  |  |  |  |
Cumulative Effect on Retained Earnings, Net of Tax |  |  |  |  |  | 11 |  |  |  |  |  |
Selling and Marketing Expense [Member] |  |  |  |  |  |  |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Deferred Policy Acquisition Costs, Amortization Expense |  |  |  |  |  | 114 |  | $ 116 |  | $ 92 |  |
Fair Value Adjustment to Acquired Loss Reserves [Member] | The Chubb Corporation [Member] |  |  |  |  |  |  |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Balance of FV adjustment on Unpaid Losses and Loss Expenses | 309 |  |  | 309 |  | 207 |  | 309 |  |  |  |
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] |  |  |  |  |  |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Effect of New Accounting Principle in Period of Adoption | 296 |  |  | 296 |  |  |  | 296 |  |  |  |
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] | Accounting Standards Update 2016-01 [Member] |  |  |  |  |  |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Effect of New Accounting Principle in Period of Adoption | (417) |  |  | (417) |  |  |  | (417) |  |  |  |
Reclassification from AOCI, Current Period, before Tax, Attributable to Parent | 454 |  |  |  |  |  |  |  |  |  |  |
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] | Accounting standards update 2018-02 [Member] |  |  |  |  |  |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Effect of New Accounting Principle in Period of Adoption |  |  |  |  |  | (121) |  |  |  |  |  |
Retained Earnings |  |  |  |  |  |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Effect of New Accounting Principle in Period of Adoption | (264) |  |  | (264) |  |  |  | $ (264) |  |  |  |
Retained Earnings | Accounting standards update 2018-02 [Member] |  |  |  |  |  |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Effect of New Accounting Principle in Period of Adoption |  |  |  |  |  | 146 |  |  |  |  |  |
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] | Accounting standards update 2018-02 [Member] |  |  |  |  |  |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Effect of New Accounting Principle in Period of Adoption |  |  |  |  |  | (47) |  |  |  |  |  |
Accumulated Foreign Currency Adjustment Attributable to Parent [Member] | Accounting standards update 2018-02 [Member] |  |  |  |  |  |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Effect of New Accounting Principle in Period of Adoption |  |  |  |  |  | 22 |  |  |  |  |  |
Scenario, Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount |  |  |  | 450 |  |  |  |  |  |  |  |
Scenario, Adjustment [Member] |  |  |  |  |  |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount |  |  |  |  |  | $ 25 |  |  |  |  |  |
Scenario, Forecast [Member] |  |  |  |  |  |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Operating Lease, Right-of-Use Asset |  |  |  |  |  |  |  |  |  |  | $ 800 |
Minimum |  |  |  |  |  |  |  |  |  |  |  |
Liability for Future Policy Benefit, by Product Segment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Interest rates used in calculating future policy benefits |  |  |  |  |  | 0.01 |  | 0.01 |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Reinsurance Premiums, Amortization Period |  |  |  |  |  | 1 year |  |  |  |  |  |
Amortization period for value of reinsurance business assumed |  |  |  |  |  | 9 years |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  | 1 year |  |  |  |  |  |
Maximum |  |  |  |  |  |  |  |  |  |  |  |
Liability for Future Policy Benefit, by Product Segment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Interest rates used in calculating future policy benefits |  |  |  |  |  | 0.11 |  | 0.08 |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Reinsurance Premiums, Amortization Period |  |  |  |  |  | 3 years |  |  |  |  |  |
Amortization period for value of reinsurance business assumed |  |  |  |  |  | 40 years |  |  |  |  |  |
Finite-Lived Intangible Asset, Useful Life |  |  |  |  |  | 30 years |  |  |  |  |  |
Affiliated notional cash pooling program |  |  |  |  |  | $ 300 |  |  |  |  |  |
Software Development [Member] |  |  |  |  |  |  |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment, Net |  |  |  |  |  | $ 970 |  |  |  |  |  |
Property, Plant and Equipment, Useful Life |  |  |  |  |  | 15 years |  |  |  |  |  |
Software Development [Member] | Minimum |  |  |  |  |  |  |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment, Useful Life |  |  |  |  |  | 3 years |  |  |  |  |  |
Software Development [Member] | Maximum |  |  |  |  |  |  |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment, Useful Life |  |  |  |  |  | 5 years |  |  |  |  |  |
Building [Member] |  |  |  |  |  |  |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment, Net |  |  |  |  |  | $ 277 |  |  |  |  |  |
Building [Member] | Maximum |  |  |  |  |  |  |  |  |  |  |  |
Summary of significant accounting policies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Property, Plant and Equipment, Useful Life |  |  |  |  |  | 39 years |  |  |  |  |  |
Structured settlements |  |  |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Deposit assets reflected in Other assets | 36 |  |  | 36 |  | $ 33 |  | $ 36 |  |  |  |
Unpaid losses and loss expenses |  |  |  |  |  | 581 |  |  |  |  |  |
Reinsurance recoverables for amounts due from life insurance companies |  |  |  |  |  | 548 |  |  |  |  |  |
Other Short-duration Insurance Product Line [Member] |  |  |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Unpaid losses and loss expenses | $ 41 |  |  | $ 41 |  | $ 40 |  | $ 41 |  |  |  |
[1] | Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2017, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.
[2] | Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2018, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

X
- Definition Borrowers collateral, percent of fair value loaned securities. + References No definition available. + Details
Name: | cb_BorrowersCollateralPercentOfFairValueLoanedSecurities
Namespace Prefix: | cb_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Deferred Marketing Costs, Amortization Period + References No definition available. + Details
Name: | cb_DeferredMarketingCostsAmortizationPeriod
Namespace Prefix: | cb_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Goodwill impairment testing, qualitative assessment, percentage probability. + References No definition available. + Details
Name: | cb_GoodwillImpairmentTestingQualitativeAssessmentPercentageProbability
Namespace Prefix: | cb_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair Value Adjustment on Acquired Unpaid Losses and Loss Expenses + References No definition available. + Details
Name: | cb_IncreaseDecreaseonAcquiredUnpaidLossesandLossExpenses
Namespace Prefix: | cb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Net operating results of ESIS included within administrative expenses. + References No definition available. + Details
Name: | cb_NetOperatingResultsOfEsisIncludedWithinAdministrativeExpenses
Namespace Prefix: | cb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Recoverable from unrated reinsurers, ceded reserve, default factor. + References No definition available. + Details
Name: | cb_RecoverableFromUnratedReinsurersCededReserveDefaultFactor
Namespace Prefix: | cb_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Reinsurance business, payment pattern of the losses assumed and range years. + References No definition available. + Details
Name: | cb_ReinsuranceBusinessPaymentPatternOfLossesAssumedAndRangeYears
Namespace Prefix: | cb_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Reinsurance Premiums, Amortization Period + References No definition available. + Details
Name: | cb_ReinsurancePremiumsAmortizationPeriod
Namespace Prefix: | cb_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Summary of significant accounting policies [Line Items]. + References No definition available. + Details
Name: | cb_SummaryOfSignificantAccountingPoliciesLineItems
Namespace Prefix: | cb_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of addition (reduction) to the amount at which an asset could be incurred (settled) in a current transaction between willing parties. + References No definition available. + Details
Name: | us-gaap_AssetsFairValueAdjustment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Carrying value as of the balance sheet date of payments made in excess of existing cash balances, which will be honored by the bank but reflected as a loan to the entity. Overdrafts generally have a very short time frame for correction or repayment and are therefore more similar to short-term bank financing than trade financing. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 45 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=99376301&loc=d3e1243-112600 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_BankOverdrafts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Carrying value as of the balance sheet date of the sum of the obligations to contract holders to provide to them an agreed upon rate of return pursuant to the terms of the underlying contract. These contracts represent lending by the contract holders to the entity in return for a guaranteed (primarily fixed) interest rate until maturity, unless called earlier if the contracts provide that option to the contract holders (usually institutions). There is little or no insurance risk for the entity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.14) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
Name: | us-gaap_BorrowingsUnderGuaranteedInvestmentAgreements
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Costs incurred to effect a business combination which have been expensed during the period. Such costs could include business integration costs, systems integration and conversion costs, and severance and other employee-related costs. + References No definition available. + Details
Name: | us-gaap_BusinessCombinationIntegrationRelatedCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption. + References No definition available. + Details
Name: | us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of the cumulative effect on retained earnings before related income tax effect. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22663-107794 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 50 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=68078379&loc=d3e122869-111746 + Details
Name: | us-gaap_CumulativeEffectOnRetainedEarningsBeforeTax1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of the cumulative effect on retained earnings net of related income tax effect. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22663-107794 + Details
Name: | us-gaap_CumulativeEffectOnRetainedEarningsNetOfTax1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of the related income tax effect of a cumulative effect on retained earnings. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22663-107794 + Details
Name: | us-gaap_CumulativeEffectOnRetainedEarningsTax1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The costs of direct-response advertising whose primary purpose is to elicit sales to customers who could be shown to have responded specifically to the advertising and that results in probable future benefits and are reported as assets net of accumulated amortization. + References Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Publisher FASB -Name Accounting Standards Codification -Topic 340 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=68067558&loc=d3e8220-108328 Reference 2: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(10)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(10)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 4: http://fasb.org/us-gaap/role/ref/otherTransitionRef -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=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DeferredAdvertisingCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of amortization expense (reversal of expense) for deferred policy acquisition costs. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 45 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6480726&loc=d3e6691-158385 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(7)(a)) -URI http://asc.fasb.org/extlink&oid=114873790&loc=SL114874131-224263 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=35755530&loc=d3e11264-158415 + Details
Name: | us-gaap_DeferredPolicyAcquisitionCostAmortizationExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The carrying amount of the asset transferred to a third party to serve as a deposit, which typically serves as security against failure by the transferor to perform under terms of an agreement. + 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 210.5-02.8,17) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DepositAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Carrying amount of liabilities as of the balance sheet date pertaining to amounts received by the insurer or reinsurer from the insured (including a ceding company) under insurance or reinsurance contracts for which insurance risk is not transferred. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 340 -SubTopic 30 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=99397363&loc=d3e9420-108338 + Details
Name: | us-gaap_DepositContractsLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 + Details
Name: | us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition A brief description of status of the tax examination, significant findings to date, and the entity's position with respect to the findings. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319 + Details
Name: | us-gaap_IncomeTaxExaminationDescription
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, attributable to increase (decrease) in the income tax rates. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 45 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=84176650&loc=d3e32059-109318 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 + Details
Name: | us-gaap_IncomeTaxReconciliationChangeInEnactedTaxRate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=99382578&loc=d3e14764-158437 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (cc) -URI http://asc.fasb.org/extlink&oid=99382578&loc=d3e14764-158437 + Details
Name: | us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense
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_LiabilityForFuturePolicyBenefitByProductSegmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Relevant interest rate assumptions that are an integral part of the methodology used in calculating the future benefits to be paid to or on behalf of policyholders and related expenses less the present value of future net premiums using assumptions such as estimates of expected investment yields, mortality, morbidity, terminations and expenses, applicable at the time the insurance contracts are made and cost of settling insured claims and cost incurred in the claim settlement process. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.13(b)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6482852&loc=d3e14931-158439 + Details
Name: | us-gaap_LiabilityForFuturePolicyBenefitsInterestRateAssumption
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
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_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of lessee's right to use underlying asset under operating lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977 + Details
Name: | us-gaap_OperatingLeaseRightOfUseAsset
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures. + 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(14)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(8)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 4: 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(13)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_PropertyPlantAndEquipmentNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount before tax of reclassification adjustments of other comprehensive income (loss) attributable to parent. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669686-108580 + Details
Name: | us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of policy benefits and costs incurred for policies assumed. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=99397103&loc=d3e6811-158387 + Details
Name: | us-gaap_ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountAssumed
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount, after valuation allowance, recoverable under reinsurance contracts including premium paid under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.(a),6) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=99397103&loc=d3e6824-158387 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 310 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=99404803&loc=d3e21409-158489 + Details
Name: | us-gaap_ReinsuranceRecoverables
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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_ShortdurationInsuranceContractsReconciliationOfClaimsDevelopmentToLiabilityLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_TaxPeriodAxis=us-gaap_TaxYear2018Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_TaxPeriodAxis=us-gaap_TaxYear2017Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=cb_TheChubbCorporationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_NewAccountingPronouncementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201708Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=us-gaap_SellingAndMarketingExpenseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=cb_FairValueAdjustmenttoAcquiredLossReservesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201601Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=cb_Accountingstandardsupdate201802Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_RetainedEarningsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedTranslationAdjustmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementScenarioAxis=us-gaap_ScenarioPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementScenarioAxis=us-gaap_ScenarioAdjustmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_SoftwareDevelopmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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