Reserve in Addition to the Account Balance, Based on Expected No-Lapse Guarantee Benefits and Expected Policy Assessments (Detail) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Liability for Future Policy Benefit, by Product Segment [Line Items]
Life policy reserves	$ 2,179	$ 2,034
Ordinary/Traditional Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Life policy reserves	671	628
Universal Life
Liability for Future Policy Benefit, by Product Segment [Line Items]
Life policy reserves	474	459
Deferred Annuities
Liability for Future Policy Benefit, by Product Segment [Line Items]
Life policy reserves	819	730
Investment Contracts
Liability for Future Policy Benefit, by Product Segment [Line Items]
Life policy reserves	198	200
Other
Liability for Future Policy Benefit, by Product Segment [Line Items]
Life policy reserves	$ 17	$ 17