Investments (Fair Values And Gross Unrealized Losses By Credit Rating Category Of ABS, MBS And Corporate Obligations) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	$ 880
Total, Unrealized Losses	(139)
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	235
Total, Unrealized Losses	(90)
Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	355
Total, Unrealized Losses	(23)
Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	290
Total, Unrealized Losses	(26)
Aaa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	277
Total, Unrealized Losses	(4)
Aaa [Member] | Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	32
Total, Unrealized Losses	(3)
Aaa [Member] | Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	214
Total, Unrealized Losses	(1)
Aaa [Member] | Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	31
Aa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	188
Total, Unrealized Losses	(16)
Aa [Member] | Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	64
Total, Unrealized Losses	(5)
Aa [Member] | Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	84
Total, Unrealized Losses	(10)
Aa [Member] | Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	40
Total, Unrealized Losses	(1)
A1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	162
Total, Unrealized Losses	(9)
A1 [Member] | Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	3
A1 [Member] | Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	1
A1 [Member] | Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	158
Total, Unrealized Losses	(9)
Baa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	74
Total, Unrealized Losses	(17)
Baa [Member] | Asset-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	(3)
Baa [Member] | Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	46
Total, Unrealized Losses	(14)
Below Investment Grade [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	164
Total, Unrealized Losses	(86)
Below Investment Grade [Member] | Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	134
Total, Unrealized Losses	(81)
Below Investment Grade [Member] | Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	15
Total, Unrealized Losses	(3)
Below Investment Grade [Member] | Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	15
Total, Unrealized Losses	(2)
Not Rated [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	15
Total, Unrealized Losses	(7)
Not Rated [Member] | Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	1
Total, Unrealized Losses	(1)
Not Rated [Member] | Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	14
Total, Unrealized Losses	$ (6)