Adoption of New Accounting Pronouncements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Item Effected [Line Items]
Decrease in deferred policy acquisition costs due to the adoption of new accounting guidance	$ 420
Decrease in deferred income tax liabilities due to the adoption of new accounting guidance	147
Decrease in shareholders' equity due to the adoption of new accounting guidance	$ 273

The decrease in deferred policy acquisition costs due to the adoption of new accounting guidance related to the accounting for costs associated with acquiring or renewing insurance contracts.

No definition available.

Name:	cb_DecreaseInDeferredPolicyAcquisitionCostsDueToAdoptionOfNewAccountingGuidance
Namespace Prefix:	cb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant