Investments and Derivative Instruments (Details 5) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	$ 2,758	$ 1,986
Less Than 12 Months, Fair Value	2,647	1,892
Less Than 12 Months, Unrealized Losses	(111)	(94)
12 Months or More, Amortized Cost	4,966	5,588
12 Months or More, Fair Value	4,435	4,851
12 Months or More, Unrealized Losses	(525)	(729)
Amortized Cost	7,724	7,574
Fair Value	7,082	6,743
Unrealized Losses	(636)	(823)
ABS [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	139	77
Less Than 12 Months, Fair Value	138	76
Less Than 12 Months, Unrealized Losses	(1)	(1)
12 Months or More, Amortized Cost	670	787
12 Months or More, Fair Value	557	616
12 Months or More, Unrealized Losses	(113)	(171)
Amortized Cost	809	864
Fair Value	695	692
Unrealized Losses	(114)	(172)
Collateralized Debt Obligations [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	4	5
Less Than 12 Months, Fair Value	3	5
Less Than 12 Months, Unrealized Losses	(1)	0
12 Months or More, Amortized Cost	1,564	1,640
12 Months or More, Fair Value	1,465	1,515
12 Months or More, Unrealized Losses	(93)	(117)
Amortized Cost	1,568	1,645
Fair Value	1,468	1,520
Unrealized Losses	(94)	(117)
CMBS [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	177	192
Less Than 12 Months, Fair Value	166	179
Less Than 12 Months, Unrealized Losses	(11)	(13)
12 Months or More, Amortized Cost	703	795
12 Months or More, Fair Value	638	701
12 Months or More, Unrealized Losses	(65)	(94)
Amortized Cost	880	987
Fair Value	804	880
Unrealized Losses	(76)	(107)
Corporate [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	1,010	614
Less Than 12 Months, Fair Value	994	578
Less Than 12 Months, Unrealized Losses	(16)	(36)
12 Months or More, Amortized Cost	1,121	1,339
12 Months or More, Fair Value	977	1,154
12 Months or More, Unrealized Losses	(144)	(185)
Amortized Cost	2,131	1,953
Fair Value	1,971	1,732
Unrealized Losses	(160)	(221)
Foreign Government Debt Securities [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	646	318
Less Than 12 Months, Fair Value	588	290
Less Than 12 Months, Unrealized Losses	(58)	(28)
12 Months or More, Amortized Cost	9	7
12 Months or More, Fair Value	7	6
12 Months or More, Unrealized Losses	(2)	(1)
Amortized Cost	655	325
Fair Value	595	296
Unrealized Losses	(60)	(29)
Municipal [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	87	65
Less Than 12 Months, Fair Value	84	62
Less Than 12 Months, Unrealized Losses	(3)	(3)
12 Months or More, Amortized Cost	88	98
12 Months or More, Fair Value	80	87
12 Months or More, Unrealized Losses	(8)	(11)
Amortized Cost	175	163
Fair Value	164	149
Unrealized Losses	(11)	(14)
RMBS [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	460	322
Less Than 12 Months, Fair Value	455	321
Less Than 12 Months, Unrealized Losses	(5)	(1)
12 Months or More, Amortized Cost	656	750
12 Months or More, Fair Value	584	636
12 Months or More, Unrealized Losses	(72)	(114)
Amortized Cost	1,116	1,072
Fair Value	1,039	957
Unrealized Losses	(77)	(115)
U.S. Treasuries [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	203	384
Less Than 12 Months, Fair Value	188	372
Less Than 12 Months, Unrealized Losses	(15)	(12)
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	203	384
Fair Value	188	372
Unrealized Losses	(15)	(12)
Fixed maturities [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	2,726	1,977
Less Than 12 Months, Fair Value	2,616	1,883
Less Than 12 Months, Unrealized Losses	(110)	(94)
12 Months or More, Amortized Cost	4,811	5,416
12 Months or More, Fair Value	4,308	4,715
12 Months or More, Unrealized Losses	(497)	(693)
Amortized Cost	7,537	7,393
Fair Value	6,924	6,598
Unrealized Losses	(607)	(787)
Equity Securities [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	32	9
Less Than 12 Months, Fair Value	31	9
Less Than 12 Months, Unrealized Losses	(1)	0
12 Months or More, Amortized Cost	155	172
12 Months or More, Fair Value	127	136
12 Months or More, Unrealized Losses	(28)	(36)
Amortized Cost	187	181
Fair Value	158	145
Unrealized Losses	$ (29)	$ (36)