| **Reserves in Addition to Account Balance, Based on Expected No-Lapse Guarantee Benefits and Expected Policy Assessments (Detail) (USD $)In Millions, unless otherwise specified** | Sep. 30, 2013 | Dec. 31, 2012 |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Liability for Future Policy Benefit, by Product Segment [Line Items]**                                                                                                           |          |          |
| Life policy and investment contract reserves                                                                                                                                       | $ 2,373       | $ 2,295       |
| Ordinary/Traditional Life                                                                                                                                                          |          |          |
| **Liability for Future Policy Benefit, by Product Segment [Line Items]**                                                                                                           |          |          |
| Life policy and investment contract reserves                                                                                                                                       | 796           | 752           |
| Universal Life                                                                                                                                                                     |          |          |
| **Liability for Future Policy Benefit, by Product Segment [Line Items]**                                                                                                           |          |          |
| Life policy and investment contract reserves                                                                                                                                       | 512           | 483           |
| Deferred Annuities                                                                                                                                                                 |          |          |
| **Liability for Future Policy Benefit, by Product Segment [Line Items]**                                                                                                           |          |          |
| Life policy and investment contract reserves                                                                                                                                       | 860           | 850           |
| Structured Settlements                                                                                                                                                             |          |          |
| **Liability for Future Policy Benefit, by Product Segment [Line Items]**                                                                                                           |          |          |
| Life policy and investment contract reserves                                                                                                                                       | 189           | 193           |
| Other                                                                                                                                                                              |          |          |
| **Liability for Future Policy Benefit, by Product Segment [Line Items]**                                                                                                           |          |          |
| Life policy and investment contract reserves                                                                                                                                       | $ 16          | $ 17          |

| X                                                                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_LiabilityForFuturePolicyBenefitByProductSegmentLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of accrued obligation to policyholders that relates to insured events under long-term life insurance contracts.
+ References
Reference 1: 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=28366191&loc=d3e13145-158430Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 13 -Subparagraph a -Article 7Reference 3: 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
+ Details**Name:**us-gaap_LiabilityForFuturePolicyBenefitsLife**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |