Invested Assets (Details 5) (USD $) In Millions	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Realized investment gains and losses [Abstract]
Fixed maturities, Gross realized gains	$ 10	$ 19	$ 23	$ 57
Fixed maturities, Gross realized losses	(4)	(6)	(15)	(11)
Fixed maturities, Other-than-temporary impairment losses	0	(2)	0	(3)
Total fixed maturities	6	11	8	43
Equity securities, Gross realized gains	10	3	29	12
Equity securities, Gross realized losses	(1)	(1)	(1)	(1)
Equity securities, Other-than-temporary impairment losses	(14)	(6)	(16)	(6)
Total equity securities	(5)	(4)	12	5
Other invested assets	68	83	209	169
Total Realized Investment Gains, Net	$ 69	$ 90	$ 229	$ 217

The gross realized gain or loss, net, for equity securities included in earnings for the period.

Name:	cb_GrossGainLossOttiEquitySecurities
Namespace Prefix:	cb
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The gross realized gain or loss, net, for fixed maturities included in earnings for the period.

+ Details

Name:	cb_GrossGainLossOttiFixedMaturities
Namespace Prefix:	cb
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This item represents the gross profit realized on the sale of equity securities categorized neither as held-to-maturity nor trading securities.

+ Details

Name:	cb_GrossRealizedGainsEquitySecurities
Namespace Prefix:	cb
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This item represents the gross profit realized on the sale of fixed maturities categorized neither as held-to-maturity nor trading securities.

+ Details

Name:	cb_GrossRealizedGainsFixedMaturities
Namespace Prefix:	cb
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This item represents the gross loss realized on the sale of equity securities categorized neither as held-to-maturity nor trading securities.

+ Details

Name:	cb_GrossRealizedLossesEquitySecurities
Namespace Prefix:	cb
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This item represents the gross loss realized on the sale of fixed maturities categorized neither as held-to-maturity nor trading securities.

+ Details

Name:	cb_GrossRealizedLossesFixedMaturities
Namespace Prefix:	cb
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount charged to income if the decline in fair value for equity securities is deemed to be other than temporary.

+ Details

Name:	cb_ImpairmentOfInvestmentsEquitySecurities
Namespace Prefix:	cb
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount charged to income if the decline in fair value for fixed maturities is deemed to be other than temporary.

+ Details

Name:	cb_ImpairmentOfInvestmentsFixedMaturities
Namespace Prefix:	cb
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This item represents the gross realized gain (loss) included in earnings for the period as a result of selling or holding other invested assets.

+ Details

Name:	cb_OtherInvestedAssetsGainLoss
Namespace Prefix:	cb
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	cb_RealizedInvestmentGainsAndLossesAbstract
Namespace Prefix:	cb
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain or loss of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain or loss which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period. Additionally, this item would include any gains or losses realized during the period from the sale of investments accounted for under the cost method of accounting and losses recognized for other than temporary impairments of the subject investments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 28

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 7
-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 13, 22

+ Details

Name:	us-gaap_GainLossOnInvestments
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration