Investments (Fair Values And Gross Unrealized Losses By Credit Rating Category Of Mortgage Backed Securities) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	$ 1,558	$ 2,387
Total, Unrealized Losses	(226)	(478)
Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	284
Total, Unrealized Losses	(63)
Mortgage-Backed Securities [Member] | Commercial Mortgage-Backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	32
Total, Unrealized Losses	(5)
Collateralized [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	123
Total, Unrealized Losses	(15)
Home Equity [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	118
Total, Unrealized Losses	(40)
Pass-Through Securities [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	3
Other RMBS [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	8
Total, Unrealized Losses	(3)
Aaa [Member] | Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	54
Aaa [Member] | Collateralized [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	49
Aaa [Member] | Home Equity [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	2
Aaa [Member] | Pass-Through Securities [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	3
Aa [Member] | Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	90
Total, Unrealized Losses	(19)
Aa [Member] | Collateralized [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	24
Total, Unrealized Losses	(3)
Aa [Member] | Home Equity [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	58
Total, Unrealized Losses	(13)
Aa [Member] | Other RMBS [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	8
Total, Unrealized Losses	(3)
A [Member] | Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	3
A [Member] | Mortgage-Backed Securities [Member] | Commercial Mortgage-Backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	2
A [Member] | Home Equity [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	1
Baa [Member] | Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	27
Total, Unrealized Losses	(4)
Baa [Member] | Mortgage-Backed Securities [Member] | Commercial Mortgage-Backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	26
Total, Unrealized Losses	(4)
Baa [Member] | Collateralized [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	1
Below Investment Grade [Member] | Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	95
Total, Unrealized Losses	(31)
Below Investment Grade [Member] | Mortgage-Backed Securities [Member] | Commercial Mortgage-Backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	4
Total, Unrealized Losses	(1)
Below Investment Grade [Member] | Collateralized [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	34
Total, Unrealized Losses	(3)
Below Investment Grade [Member] | Home Equity [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	57
Total, Unrealized Losses	(27)
Not Rated [Member] | Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	15
Total, Unrealized Losses	(9)
Not Rated [Member] | Collateralized [Member] | Mortgage-Backed Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	15
Total, Unrealized Losses	$ (9)