Name:	cb_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainLossBeforeTax
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Amount before tax of unrealized gain or (loss) net in accumulated other comprehensive income (AOCI) on investments in equity securities classified as available-for-sale.

No definition available.

Name:	cb_AvailableForSaleEquitySecuritiesAccumulatedGrossUnrealizedGainLossBeforeTax
Namespace Prefix:	cb_
Data Type:	xbrli:monetaryItemType
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The amount for all deferred tax assets and liabilities relating to unrealized appreciation or depreciation as of the balance sheet date.

No definition available.

Name:	cb_DeferredIncomeTaxAssetLiability
Namespace Prefix:	cb_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

The net excess or deficiency of the fair value of fixed maturities and equity securities over or under its amortized cost which has not been recognized in earnings of the entity net of deferred income tax.

No definition available.

Name:	cb_FixedMaturitiesAndEquitySecuritiesUnrealizedAppreciationDepreciationNetOfTax
Namespace Prefix:	cb_
Data Type:	xbrli:monetaryItemType
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

Name:	us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

Name:	us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in equity securities classified as available-for-sale.

Name:	us-gaap_AvailableForSaleEquitySecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in equity securities classified as available-for-sale.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

Name:	us-gaap_AvailableForSaleEquitySecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount before tax of unrealized gain (loss) in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

No definition available.