Fair Values of Financial Instruments (Details 2)	Jun. 30, 2011
Fair Values of Financial Instruments (Textual) [Abstract]
Percentage of fair value amounts for fixed maturities provided by a pricing service	99.00%

Name:

cb_PercentageOfFairValueAmountsForFixedMaturitiesProvidedByPricingService

Namespace Prefix:

cb

Data Type:

us-types:percentItemType

Balance Type:

na

Period Type:

instant