Investments (Fair Values And Gross Unrealized Losses By Credit Rating Category Of Asset Backed Securities) (Details) (USD $) In Millions	Sep. 30, 2011		Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	$ 2,549		$ 6,954
Total, Unrealized Losses	(567)		(804)
Asset-Backed Securities [Member] | ABS CDO [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	116
Total, Unrealized Losses	(61)
Asset-Backed Securities [Member] | ABS CDO [Member] | Aaa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	74
Total, Unrealized Losses	(1)
Asset-Backed Securities [Member] | ABS CDO [Member] | Aa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	5
Asset-Backed Securities [Member] | ABS CDO [Member] | A [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	7
Total, Unrealized Losses	(2)
Asset-Backed Securities [Member] | ABS CDO [Member] | Baa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	1
Total, Unrealized Losses	(3)
Asset-Backed Securities [Member] | ABS CDO [Member] | Below Investment Grade [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	29
Total, Unrealized Losses	(55)
Asset-Backed Securities [Member] | Corporate CDO [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	236
Total, Unrealized Losses	(90)
Asset-Backed Securities [Member] | Corporate CDO [Member] | Aaa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	48
Total, Unrealized Losses	(7)
Asset-Backed Securities [Member] | Corporate CDO [Member] | Aa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	13
Total, Unrealized Losses	(1)
Asset-Backed Securities [Member] | Corporate CDO [Member] | A [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	69
Total, Unrealized Losses	(10)
Asset-Backed Securities [Member] | Corporate CDO [Member] | Baa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	21
Total, Unrealized Losses	(9)
Asset-Backed Securities [Member] | Corporate CDO [Member] | Below Investment Grade [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	61
Total, Unrealized Losses	(59)
Asset-Backed Securities [Member] | Corporate CDO [Member] | Not Rated [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	24
Total, Unrealized Losses	(4)
Asset-Backed Securities [Member] | Auto Loans [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	15
Asset-Backed Securities [Member] | Auto Loans [Member] | Aa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	2
Asset-Backed Securities [Member] | Auto Loans [Member] | Below Investment Grade [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	13
Asset-Backed Securities [Member] | Credit Cards [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	3
Asset-Backed Securities [Member] | Credit Cards [Member] | Aaa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	3
Asset-Backed Securities [Member] | Equipment Leases [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	30
Total, Unrealized Losses	(3)
Asset-Backed Securities [Member] | Equipment Leases [Member] | Aaa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	1
Asset-Backed Securities [Member] | Equipment Leases [Member] | Baa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	29
Total, Unrealized Losses	(3)
Asset-Backed Securities [Member] | Small Business/ Student Loans [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	30
Total, Unrealized Losses	(4)
Asset-Backed Securities [Member] | Small Business/ Student Loans [Member] | Aaa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	18
Total, Unrealized Losses	(3)
Asset-Backed Securities [Member] | Small Business/ Student Loans [Member] | Below Investment Grade [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	12
Total, Unrealized Losses	(1)
Asset-Backed Securities [Member] | Other ABS [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	293
Total, Unrealized Losses	(127)
Asset-Backed Securities [Member] | Other ABS [Member] | Aaa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	12
Asset-Backed Securities [Member] | Other ABS [Member] | Aa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	32
Total, Unrealized Losses	(4)
Asset-Backed Securities [Member] | Other ABS [Member] | A [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	58
Total, Unrealized Losses	(11)
Asset-Backed Securities [Member] | Other ABS [Member] | Baa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	43
Total, Unrealized Losses	(6)
Asset-Backed Securities [Member] | Other ABS [Member] | Below Investment Grade [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	115
Total, Unrealized Losses	(9)
Asset-Backed Securities [Member] | Other ABS [Member] | Not Rated [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	33
Total, Unrealized Losses	(97)
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	723
Total, Unrealized Losses	(285)
Asset-Backed Securities [Member] | MBIA [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	323	[1]
Total, Unrealized Losses	80	[1]
Asset-Backed Securities [Member] | Aaa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	156
Total, Unrealized Losses	(11)
Asset-Backed Securities [Member] | Aa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	52
Total, Unrealized Losses	(5)
Asset-Backed Securities [Member] | A [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	134
Total, Unrealized Losses	(23)
Asset-Backed Securities [Member] | Baa [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	94
Total, Unrealized Losses	(21)
Asset-Backed Securities [Member] | Below Investment Grade [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	230
Total, Unrealized Losses	(124)
Asset-Backed Securities [Member] | Not Rated [Member]
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	57
Total, Unrealized Losses	$ (101)

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