| **Reserves in Addition to Account Balance, Based on Expected No-Lapse Guarantee Benefits and Expected Policy Assessments (Detail) (USD $)In Millions, unless otherwise specified** | Mar. 31, 2013 | Dec. 31, 2012 |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Liability for Future Policy Benefit, by Product Segment [Line Items]**                                                                                                           |          |          |
| Life policy and investment contract reserves                                                                                                                                       | $ 2,310       | $ 2,295       |
| Ordinary/Traditional Life                                                                                                                                                          |          |          |
| **Liability for Future Policy Benefit, by Product Segment [Line Items]**                                                                                                           |          |          |
| Life policy and investment contract reserves                                                                                                                                       | 760           | 752           |
| Universal Life                                                                                                                                                                     |          |          |
| **Liability for Future Policy Benefit, by Product Segment [Line Items]**                                                                                                           |          |          |
| Life policy and investment contract reserves                                                                                                                                       | 487           | 483           |
| Deferred Annuities                                                                                                                                                                 |          |          |
| **Liability for Future Policy Benefit, by Product Segment [Line Items]**                                                                                                           |          |          |
| Life policy and investment contract reserves                                                                                                                                       | 852           | 850           |
| Structured Settlements                                                                                                                                                             |          |          |
| **Liability for Future Policy Benefit, by Product Segment [Line Items]**                                                                                                           |          |          |
| Life policy and investment contract reserves                                                                                                                                       | 194           | 193           |
| Other                                                                                                                                                                              |          |          |
| **Liability for Future Policy Benefit, by Product Segment [Line Items]**                                                                                                           |          |          |
| Life policy and investment contract reserves                                                                                                                                       | $ 17          | $ 17          |

| X                                                                                                                                                                                            |
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| - Details**Name:**us-gaap_LiabilityForFuturePolicyBenefitByProductSegmentLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
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| - Definition
The sum of the known and estimated amounts payable as of the balance sheet date to life insurance policyholders that relates to insured events which can be viewed as either (a) the present value of future benefits to be paid to or on behalf of policyholders and expenses less the present value of future net premiums payable under the insurance contracts or (b) the accumulated amount of net premiums already collected less the accumulated amount of benefits and expenses already paid to or on behalf of policyholders.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 60 -Paragraph 21-26 -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 40 -Section 25 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=6482067&loc=d3e13145-158430Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 13 -Subparagraph a -Article 7Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.13(a)(1)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910
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