Reserve for Life-Contingent Contract Benefits and Contractholder Funds (Details 6) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Liabilities for guarantees:
Liability for guarantees	$ 673	$ 644	$ 599
Liability for guarantees related to income benefits
Liabilities for guarantees:
Liability for guarantees	235	191	227
Variable annuities | In the event of death
Liabilities for guarantees:
Liability for guarantees	112	116	85
Variable annuities | Liability for guarantees related to income benefits
Liabilities for guarantees:
Liability for guarantees	221	175	211
Variable annuities | Accumulation at specified dates
Liabilities for guarantees:
Liability for guarantees	86	105	88
Variable annuities | For cumulative periodic withdrawals
Liabilities for guarantees:
Liability for guarantees	39	57	47
Variable annuities | Other guarantees
Liabilities for guarantees:
Liability for guarantees	$ 215	$ 191	$ 168