Incurred Consolidated Property Casualty Insurance Loss and Loss Expenses on Assumed and Ceded Business (Detail) (USD $) In Millions	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Ceded contract holders' benefits incurred		$ (33)		$ (44)
Net incurred loss and loss expenses	801	595	1,376	1,111
Property, Liability and Casualty Insurance Segment
Direct incurred loss and loss expenses	981	528	1,508	977
Assumed incurred loss and loss expenses	5	3	20	5
Ceded contract holders' benefits incurred	(229)	21	(241)	44
Net incurred loss and loss expenses	$ 757	$ 552	$ 1,287	$ 1,026

Total provision in the period for future policy benefits, claims incurred and costs incurred in the claims settlement process before the effects of reinsurance arrangements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Paragraph 5
-Article 7

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.5)
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Provision for benefits, claims and claims settlement expenses incurred during the period net of the effects of contracts assumed and ceded.

+ References

+ Details

Name:	us-gaap_PolicyholderBenefitsAndClaimsIncurredNet
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of the provision for the period for claims and benefits incurred on contract risks assumed from other (ceding) insurers under reinsurance arrangements.

+ References

+ Details

Name:	us-gaap_ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountAssumed
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The reduction in the amount of the provision for the period for claims and benefits incurred on contract risks ceded to other insurers under reinsurance arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 113
-Paragraph 27, 113
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6811-158387

+ Details

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