Reinsurance - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012 Reinsurer	Dec. 31, 2011	Dec. 31, 2010
Reinsurance [Line Items]
Reinsurance recoverables included in other long-term assets	$ 461	$ 436
Percentage of reinsurance recoverables resulting from 100% coinsurance agreements	48.00%	51.00%
Premiums ceded	34	34	34
Number of reinsurers comprising other reinsurance recoverables balance	15
Maximum carrying value of reinsurance recoverables for a number of reinsurers	20
Number of reinsurers who have placed cash and securities in trusts	2
Cash and securities in trusts held by certain reinsurers	$ 24
100% Coinsurance Agreements
Reinsurance [Line Items]
Percentage of coinsurance agreement	100.00%	100.00%

Amount held in cash and securities in trust, at least equal to the recoverable from the reinsurer

No definition available.

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- Definition

Maximum carrying value of reinsurance recoverables for a number of reinsurers

+ References

No definition available.

+ Details

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- Definition

Number of reinsurers comprising other reinsurance recoverables balance

+ References

No definition available.

+ Details

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- Definition

Number of reinsurers who have placed cash and securities in trusts

+ References

No definition available.

+ Details

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- Definition

Percentage Of Coinsurance Agreement

+ References

No definition available.

+ Details

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- Details

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- Definition

Percentage of reinsurance recoverables resulting from 100% coinsurance agreements

+ References

No definition available.

+ Details

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- Definition

Total consideration paid and payable to reinsurers during the period pursuant to terms of reinsurance arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 17

-Article 12

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 605

-Section 50

-Paragraph 1

-Subparagraph (b),(c)(2)

-URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 113

-Paragraph 27

-Subparagraph a, b

-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.

+ Details

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- Definition

The known and estimated amount recoverable as of the balance sheet date from reinsurers for claims paid or incurred by the ceding insurer and associated claims settlement expenses, including estimated amounts for claims incurred but not reported, and policy benefits, net of any related valuation allowance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 113

-Paragraph 14, 16, 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 SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 6

-Article 7

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 20

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6824-158387

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.(a),6)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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