Name:	cb_CombinedLossAndExpenseRatioExcludingImpactOfStormSandy
Namespace Prefix:	cb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The amount of net income (loss) related to Storm Sandy for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

No definition available.

Name:	cb_EarningsPerShareBasicReductionDueToStormSandy
Namespace Prefix:	cb_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

The amount of net income (loss) related to Storm Sandy for the period per each share of common stock or unit outstanding during the reporting period.

No definition available.

Name:	cb_EarningsPerShareDilutedReductionDueToStormSandy
Namespace Prefix:	cb_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

Represents the ratio of statutory underwriting expenses to premiums written less dividends to policyholders excluding the impact of Storm Sandy.

No definition available.

Name:	cb_ExpensesToPremiumsWrittenExcludingImpactOfStormSandy
Namespace Prefix:	cb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents the ratio of losses and loss expenses to premiums earned less dividends to policyholders excluding the impact of Storm Sandy.

No definition available.

Name:	cb_LossesToPremiumsEarnedExcludingImpactOfStormSandy
Namespace Prefix:	cb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The portion of net income (loss) for the period which is attributable to Storm Sandy.

No definition available.

Name:	cb_NetIncomeReductionDueToStormSandy
Namespace Prefix:	cb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The amount of losses recognized during the period related to Storm Sandy.

No definition available.

Name:	cb_NetLossesDueToStormSandy
Namespace Prefix:	cb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The amount of reinstatement premium costs recognized during the period related to Storm Sandy.

No definition available.