Investments (Fair Values And Gross Unrealized Losses By Credit Rating Category Of Mortgage Backed Securities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Investment [Line Items]
Total, Fair Value	$ 2,387	$ 6,954
Total, Unrealized Losses	(478)	(804)
Mortgage-Backed Securities [Member]
Investment [Line Items]
Total, Fair Value	401
Total, Unrealized Losses	(119)
Mortgage-Backed Securities [Member] | Aaa [Member]
Investment [Line Items]
Total, Fair Value	93
Total, Unrealized Losses
Mortgage-Backed Securities [Member] | Aa [Member]
Investment [Line Items]
Total, Fair Value	129
Total, Unrealized Losses	(36)
Mortgage-Backed Securities [Member] | A [Member]
Investment [Line Items]
Total, Fair Value	13
Total, Unrealized Losses	(1)
Mortgage-Backed Securities [Member] | Baa [Member]
Investment [Line Items]
Total, Fair Value	25
Total, Unrealized Losses	(9)
Mortgage-Backed Securities [Member] | Below Investment Grade [Member]
Investment [Line Items]
Total, Fair Value	126
Total, Unrealized Losses	(61)
Mortgage-Backed Securities [Member] | Not Rated [Member]
Investment [Line Items]
Total, Fair Value	15
Total, Unrealized Losses	(12)
Commercial Mortgage Backed [Member] | Mortgage-Backed Securities [Member]
Investment [Line Items]
Total, Fair Value	30
Total, Unrealized Losses	(10)
Commercial Mortgage Backed [Member] | Mortgage-Backed Securities [Member] | Aaa [Member]
Investment [Line Items]
Total, Fair Value	2
Total, Unrealized Losses
Commercial Mortgage Backed [Member] | Mortgage-Backed Securities [Member] | Aa [Member]
Investment [Line Items]
Total, Fair Value	1
Total, Unrealized Losses
Commercial Mortgage Backed [Member] | Mortgage-Backed Securities [Member] | A [Member]
Investment [Line Items]
Total, Fair Value	2
Total, Unrealized Losses
Commercial Mortgage Backed [Member] | Mortgage-Backed Securities [Member] | Baa [Member]
Investment [Line Items]
Total, Fair Value	23
Total, Unrealized Losses	(9)
Commercial Mortgage Backed [Member] | Mortgage-Backed Securities [Member] | Below Investment Grade [Member]
Investment [Line Items]
Total, Fair Value	1
Total, Unrealized Losses	(1)
Commercial Mortgage Backed [Member] | Mortgage-Backed Securities [Member] | Not Rated [Member]
Investment [Line Items]
Total, Fair Value	1
Total, Unrealized Losses
Residential Mortgage-Backed Securities [Member] | Collateralized [Member] | Mortgage-Backed Securities [Member]
Investment [Line Items]
Total, Fair Value	167
Total, Unrealized Losses	(39)
Residential Mortgage-Backed Securities [Member] | Collateralized [Member] | Mortgage-Backed Securities [Member] | Aaa [Member]
Investment [Line Items]
Total, Fair Value	69
Total, Unrealized Losses
Residential Mortgage-Backed Securities [Member] | Collateralized [Member] | Mortgage-Backed Securities [Member] | Aa [Member]
Investment [Line Items]
Total, Fair Value	39
Total, Unrealized Losses	(10)
Residential Mortgage-Backed Securities [Member] | Collateralized [Member] | Mortgage-Backed Securities [Member] | A [Member]
Investment [Line Items]
Total, Fair Value	10
Total, Unrealized Losses	(1)
Residential Mortgage-Backed Securities [Member] | Collateralized [Member] | Mortgage-Backed Securities [Member] | Baa [Member]
Investment [Line Items]
Total, Fair Value	2
Total, Unrealized Losses
Residential Mortgage-Backed Securities [Member] | Collateralized [Member] | Mortgage-Backed Securities [Member] | Below Investment Grade [Member]
Investment [Line Items]
Total, Fair Value	34
Total, Unrealized Losses	(16)
Residential Mortgage-Backed Securities [Member] | Collateralized [Member] | Mortgage-Backed Securities [Member] | Not Rated [Member]
Investment [Line Items]
Total, Fair Value	13
Total, Unrealized Losses	(12)
Residential Mortgage-Backed Securities [Member] | Home Equity [Member] | Mortgage-Backed Securities [Member]
Investment [Line Items]
Total, Fair Value	168
Total, Unrealized Losses	(62)
Residential Mortgage-Backed Securities [Member] | Home Equity [Member] | Mortgage-Backed Securities [Member] | Aaa [Member]
Investment [Line Items]
Total, Fair Value	2
Total, Unrealized Losses
Residential Mortgage-Backed Securities [Member] | Home Equity [Member] | Mortgage-Backed Securities [Member] | Aa [Member]
Investment [Line Items]
Total, Fair Value	80
Total, Unrealized Losses	(22)
Residential Mortgage-Backed Securities [Member] | Home Equity [Member] | Mortgage-Backed Securities [Member] | A [Member]
Investment [Line Items]
Total, Fair Value	1
Total, Unrealized Losses
Residential Mortgage-Backed Securities [Member] | Home Equity [Member] | Mortgage-Backed Securities [Member] | Baa [Member]
Investment [Line Items]
Total, Fair Value
Total, Unrealized Losses
Residential Mortgage-Backed Securities [Member] | Home Equity [Member] | Mortgage-Backed Securities [Member] | Below Investment Grade [Member]
Investment [Line Items]
Total, Fair Value	84
Total, Unrealized Losses	(40)
Residential Mortgage-Backed Securities [Member] | Home Equity [Member] | Mortgage-Backed Securities [Member] | Not Rated [Member]
Investment [Line Items]
Total, Fair Value	1
Total, Unrealized Losses
Residential Mortgage-Backed Securities [Member] | Pass-Through Securities [Member] | Mortgage-Backed Securities [Member]
Investment [Line Items]
Total, Fair Value	20
Total, Unrealized Losses
Residential Mortgage-Backed Securities [Member] | Pass-Through Securities [Member] | Mortgage-Backed Securities [Member] | Aaa [Member]
Investment [Line Items]
Total, Fair Value	20
Total, Unrealized Losses
Residential Mortgage-Backed Securities [Member] | Pass-Through Securities [Member] | Mortgage-Backed Securities [Member] | Aa [Member]
Investment [Line Items]
Total, Fair Value
Total, Unrealized Losses
Residential Mortgage-Backed Securities [Member] | Pass-Through Securities [Member] | Mortgage-Backed Securities [Member] | A [Member]
Investment [Line Items]
Total, Fair Value
Total, Unrealized Losses
Residential Mortgage-Backed Securities [Member] | Pass-Through Securities [Member] | Mortgage-Backed Securities [Member] | Baa [Member]
Investment [Line Items]
Total, Fair Value
Total, Unrealized Losses
Residential Mortgage-Backed Securities [Member] | Pass-Through Securities [Member] | Mortgage-Backed Securities [Member] | Below Investment Grade [Member]
Investment [Line Items]
Total, Fair Value
Total, Unrealized Losses
Residential Mortgage-Backed Securities [Member] | Pass-Through Securities [Member] | Mortgage-Backed Securities [Member] | Not Rated [Member]
Investment [Line Items]
Total, Fair Value
Total, Unrealized Losses
Residential Mortgage-Backed Securities [Member] | Other RMBS [Member] | Mortgage-Backed Securities [Member]
Investment [Line Items]
Total, Fair Value	16
Total, Unrealized Losses	(8)
Residential Mortgage-Backed Securities [Member] | Other RMBS [Member] | Mortgage-Backed Securities [Member] | Aaa [Member]
Investment [Line Items]
Total, Fair Value
Total, Unrealized Losses
Residential Mortgage-Backed Securities [Member] | Other RMBS [Member] | Mortgage-Backed Securities [Member] | Aa [Member]
Investment [Line Items]
Total, Fair Value	9
Total, Unrealized Losses	(4)
Residential Mortgage-Backed Securities [Member] | Other RMBS [Member] | Mortgage-Backed Securities [Member] | A [Member]
Investment [Line Items]
Total, Fair Value
Total, Unrealized Losses
Residential Mortgage-Backed Securities [Member] | Other RMBS [Member] | Mortgage-Backed Securities [Member] | Baa [Member]
Investment [Line Items]
Total, Fair Value
Total, Unrealized Losses
Residential Mortgage-Backed Securities [Member] | Other RMBS [Member] | Mortgage-Backed Securities [Member] | Below Investment Grade [Member]
Investment [Line Items]
Total, Fair Value	7
Total, Unrealized Losses	(4)
Residential Mortgage-Backed Securities [Member] | Other RMBS [Member] | Mortgage-Backed Securities [Member] | Not Rated [Member]
Investment [Line Items]
Total, Fair Value
Total, Unrealized Losses