Investments and Derivative Instruments (Details 5) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	$ 9,115	$ 7,837
Less Than 12 Months, Fair Value	8,708	7,381
Less Than 12 Months, Unrealized Losses	(407)	(456)
12 Months or More, Amortized Cost	10,808	11,613
12 Months or More, Fair Value	8,955	9,324
12 Months or More, Unrealized Losses	(1,811)	(2,218)
Amortized Cost	19,923	19,450
Fair Value	17,663	16,705
Unrealized Losses	(2,218)	(2,674)
ABS [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	192	629
Less Than 12 Months, Fair Value	159	594
Less Than 12 Months, Unrealized Losses	(33)	(35)
12 Months or More, Amortized Cost	1,098	1,169
12 Months or More, Fair Value	825	872
12 Months or More, Unrealized Losses	(273)	(297)
Amortized Cost	1,290	1,798
Fair Value	984	1,466
Unrealized Losses	(306)	(332)
CDOs [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	62	81
Less Than 12 Months, Fair Value	42	59
Less Than 12 Months, Unrealized Losses	(20)	(22)
12 Months or More, Amortized Cost	3,187	2,709
12 Months or More, Fair Value	2,860	2,383
12 Months or More, Unrealized Losses	(285)	(326)
Amortized Cost	3,249	2,790
Fair Value	2,902	2,442
Unrealized Losses	(305)	(348)
CMBS [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	852	1,297
Less Than 12 Months, Fair Value	803	1,194
Less Than 12 Months, Unrealized Losses	(49)	(103)
12 Months or More, Amortized Cost	1,955	2,144
12 Months or More, Fair Value	1,626	1,735
12 Months or More, Unrealized Losses	(329)	(409)
Amortized Cost	2,807	3,441
Fair Value	2,429	2,929
Unrealized Losses	(378)	(512)
Corporate [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	4,076	4,388
Less Than 12 Months, Fair Value	3,941	4,219
Less Than 12 Months, Unrealized Losses	(135)	(169)
12 Months or More, Amortized Cost	2,543	3,268
12 Months or More, Fair Value	2,116	2,627
12 Months or More, Unrealized Losses	(427)	(570)
Amortized Cost	6,619	7,656
Fair Value	6,057	6,846
Unrealized Losses	(562)	(739)
Foreign govt./govt. agencies [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	647	218
Less Than 12 Months, Fair Value	627	212
Less Than 12 Months, Unrealized Losses	(20)	(6)
12 Months or More, Amortized Cost	29	51
12 Months or More, Fair Value	25	47
12 Months or More, Unrealized Losses	(4)	(4)
Amortized Cost	676	269
Fair Value	652	259
Unrealized Losses	(24)	(10)
Municipal [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	823	299
Less Than 12 Months, Fair Value	799	294
Less Than 12 Months, Unrealized Losses	(24)	(5)
12 Months or More, Amortized Cost	425	627
12 Months or More, Fair Value	382	560
12 Months or More, Unrealized Losses	(43)	(67)
Amortized Cost	1,248	926
Fair Value	1,181	854
Unrealized Losses	(67)	(72)
RMBS [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	1,246	415
Less Than 12 Months, Fair Value	1,166	330
Less Than 12 Months, Unrealized Losses	(80)	(85)
12 Months or More, Amortized Cost	1,171	1,206
12 Months or More, Fair Value	828	835
12 Months or More, Unrealized Losses	(343)	(371)
Amortized Cost	2,417	1,621
Fair Value	1,994	1,165
Unrealized Losses	(423)	(456)
U.S. Treasuries [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	1,011	343
Less Than 12 Months, Fair Value	990	341
Less Than 12 Months, Unrealized Losses	(21)	(2)
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	1,011	343
Fair Value	990	341
Unrealized Losses	(21)	(2)
Fixed maturities [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	8,909	7,670
Less Than 12 Months, Fair Value	8,527	7,243
Less Than 12 Months, Unrealized Losses	(382)	(427)
12 Months or More, Amortized Cost	10,408	11,174
12 Months or More, Fair Value	8,662	9,059
12 Months or More, Unrealized Losses	(1,704)	(2,044)
Amortized Cost	19,317	18,844
Fair Value	17,189	16,302
Unrealized Losses	(2,086)	(2,471)
Equity Securities [Member]
Security Unrealized Loss Aging
Less Than 12 Months, Amortized Cost	206	167
Less Than 12 Months, Fair Value	181	138
Less Than 12 Months, Unrealized Losses	(25)	(29)
12 Months or More, Amortized Cost	400	439
12 Months or More, Fair Value	293	265
12 Months or More, Unrealized Losses	(107)	(174)
Amortized Cost	606	606
Fair Value	474	403
Unrealized Losses	$ (132)	$ (203)