Life Insurance Contract Holders' Benefits Incurred on Ceded Business (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net incurred loss and loss expenses	$ 2,524	$ 2,180	$ 2,242
Life Insurance Segment
Direct contract holders' benefits incurred	232	233	201
Assumed contract holders' benefits incurred
Ceded contract holders' benefits incurred	(43)	(63)	(41)
Net incurred loss and loss expenses	$ 189	$ 170	$ 160

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

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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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration