Investments and Derivative Instruments (Details 5) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Document Period End Date	Mar. 31, 2013
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	$ 6,281	$ 4,981
Less Than 12 Months, Fair Value	6,108	4,855
Less Than 12 Months, Unrealized Losses	(173)	(126)
12 Months or More, Amortized Cost	6,983	7,850
12 Months or More, Fair Value	6,299	6,894
12 Months or More, Unrealized Losses	(669)	(936)
Amortized Cost	13,264	12,831
Fair Value	12,407	11,749
Unrealized Losses	(842)	(1,062)
ABS [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	361	163
Less Than 12 Months, Fair Value	360	161
Less Than 12 Months, Unrealized Losses	(1)	(2)
12 Months or More, Amortized Cost	716	886
12 Months or More, Fair Value	597	705
12 Months or More, Unrealized Losses	(119)	(181)
Amortized Cost	1,077	1,049
Fair Value	957	866
Unrealized Losses	(120)	(183)
Collateralized Debt Obligations [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	4	5
Less Than 12 Months, Fair Value	3	4
Less Than 12 Months, Unrealized Losses	(1)	(1)
12 Months or More, Amortized Cost	2,481	2,567
12 Months or More, Fair Value	2,342	2,389
12 Months or More, Unrealized Losses	(124)	(158)
Amortized Cost	2,485	2,572
Fair Value	2,345	2,393
Unrealized Losses	(125)	(159)
CMBS [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	359	339
Less Than 12 Months, Fair Value	342	322
Less Than 12 Months, Unrealized Losses	(17)	(17)
12 Months or More, Amortized Cost	1,064	1,248
12 Months or More, Fair Value	961	1,086
12 Months or More, Unrealized Losses	(103)	(162)
Amortized Cost	1,423	1,587
Fair Value	1,303	1,408
Unrealized Losses	(120)	(179)
Corporate [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	1,815	1,261
Less Than 12 Months, Fair Value	1,779	1,218
Less Than 12 Months, Unrealized Losses	(36)	(43)
12 Months or More, Amortized Cost	1,569	1,823
12 Months or More, Fair Value	1,385	1,590
12 Months or More, Unrealized Losses	(184)	(233)
Amortized Cost	3,384	3,084
Fair Value	3,164	2,808
Unrealized Losses	(220)	(276)
Foreign Government Debt Securities [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	982	1,380
Less Than 12 Months, Fair Value	913	1,343
Less Than 12 Months, Unrealized Losses	(69)	(37)
12 Months or More, Amortized Cost	16	20
12 Months or More, Fair Value	13	17
12 Months or More, Unrealized Losses	(3)	(3)
Amortized Cost	998	1,400
Fair Value	926	1,360
Unrealized Losses	(72)	(40)
Municipal [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	403	271
Less Than 12 Months, Fair Value	394	265
Less Than 12 Months, Unrealized Losses	(9)	(6)
12 Months or More, Amortized Cost	106	157
12 Months or More, Fair Value	97	144
12 Months or More, Unrealized Losses	(9)	(13)
Amortized Cost	509	428
Fair Value	491	409
Unrealized Losses	(18)	(19)
RMBS [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	1,863	910
Less Than 12 Months, Fair Value	1,844	908
Less Than 12 Months, Unrealized Losses	(19)	(2)
12 Months or More, Amortized Cost	771	869
12 Months or More, Fair Value	686	738
12 Months or More, Unrealized Losses	(85)	(131)
Amortized Cost	2,634	1,779
Fair Value	2,530	1,646
Unrealized Losses	(104)	(133)
U.S. Treasuries [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	423	583
Less Than 12 Months, Fair Value	404	567
Less Than 12 Months, Unrealized Losses	(19)	(16)
12 Months or More, Amortized Cost	0	0
12 Months or More, Fair Value	0	0
12 Months or More, Unrealized Losses	0	0
Amortized Cost	423	583
Fair Value	404	567
Unrealized Losses	(19)	(16)
Fixed maturities [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	6,210	4,912
Less Than 12 Months, Fair Value	6,039	4,788
Less Than 12 Months, Unrealized Losses	(171)	(124)
12 Months or More, Amortized Cost	6,723	7,570
12 Months or More, Fair Value	6,081	6,669
12 Months or More, Unrealized Losses	(627)	(881)
Amortized Cost	12,933	12,482
Fair Value	12,120	11,457
Unrealized Losses	(798)	(1,005)
Equity Securities [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	71	69
Less Than 12 Months, Fair Value	69	67
Less Than 12 Months, Unrealized Losses	(2)	(2)
12 Months or More, Amortized Cost	260	280
12 Months or More, Fair Value	218	225
12 Months or More, Unrealized Losses	(42)	(55)
Amortized Cost	331	349
Fair Value	287	292
Unrealized Losses	$ (44)	$ (57)