Credit Risk (Details 4) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 contract Y	Mar. 31, 2011	Dec. 31, 2011
Credit Risk
Number of contracts through which the entity has exposure to consumer credit risk	2
Contractual reinsurance period for each pool (in years)	10
Weighted-average reinsurance period (in years)	4
Cash and securities in trust related to potential obligation	$ 205
Unpaid reinsurance losses outstanding	7
Summary of the activity in reinsurance-related reserves
Balance, beginning of period	84	113
Realized reinsurance losses	(18)	(16)
Increase in liability for reinsurance losses	6	13
Balance, end of period	72	110
Receivables greater than 90 days past due	5		16
Receivables greater than 90 days past due and still accruing interest	$ 5		$ 16