Investments (Fair Values And Gross Unrealized Losses By Credit Rating Category Of Corporate Obligations) (Details) (USD $) In Millions	Sep. 30, 2011		Dec. 31, 2010
Investment [Line Items]
Total, Fair Value	$ 2,549		$ 6,954
Total, Unrealized Losses	567		804
Corporate Obligations [Member]
Investment [Line Items]
Total, Fair Value	774
Total, Unrealized Losses	(109)
Corporate Obligations [Member] | MBIA [Member]
Investment [Line Items]
Total, Fair Value	135	[1]
Total, Unrealized Losses	(19)	[1]
Corporate Obligations [Member] | Aaa [Member]
Investment [Line Items]
Total, Fair Value	70
Total, Unrealized Losses
Corporate Obligations [Member] | Aa [Member]
Investment [Line Items]
Total, Fair Value	156
Total, Unrealized Losses	(26)
Corporate Obligations [Member] | A [Member]
Investment [Line Items]
Total, Fair Value	189
Total, Unrealized Losses	(26)
Corporate Obligations [Member] | Baa [Member]
Investment [Line Items]
Total, Fair Value	232
Total, Unrealized Losses	(27)
Corporate Obligations [Member] | Below Investment Grade [Member]
Investment [Line Items]
Total, Fair Value	104
Total, Unrealized Losses	(24)
Corporate Obligations [Member] | Not Rated [Member]
Investment [Line Items]
Total, Fair Value	23
Total, Unrealized Losses	$ (6)

[1] Includes investments insured by MBIA Corp. and National.