Investments (Details 10) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012 security	Dec. 31, 2011 security
Fixed income and equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	281	459
Fair value, continuous unrealized loss position for less than 12 months	$ 1,780	$ 2,936
Unrealized losses, continuous unrealized loss position for less than 12 months	(73)	(146)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	469	534
Fair value, continuous unrealized loss position for 12 months or more	3,652	4,139
Unrealized losses, continuous unrealized loss position for 12 months or more	(789)	(1,116)
Total unrealized losses
Total unrealized losses	(862)	(1,262)
Fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	277	456
Fair value, continuous unrealized loss position for less than 12 months	1,763	2,901
Unrealized losses, continuous unrealized loss position for less than 12 months	(73)	(144)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	469	534
Fair value, continuous unrealized loss position for 12 months or more	3,652	4,139
Unrealized losses, continuous unrealized loss position for 12 months or more	(789)	(1,116)
Total unrealized losses
Gross unrealized losses	(862)	(1,260)
U.S. government and agencies
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	2
Fair value, continuous unrealized loss position for less than 12 months	160
Municipal
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	12	8
Fair value, continuous unrealized loss position for less than 12 months	104	67
Unrealized losses, continuous unrealized loss position for less than 12 months	(4)	(7)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	71	97
Fair value, continuous unrealized loss position for 12 months or more	526	624
Unrealized losses, continuous unrealized loss position for 12 months or more	(81)	(107)
Total unrealized losses
Total unrealized losses	(85)	(114)
Corporate
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	118	226
Fair value, continuous unrealized loss position for less than 12 months	1,141	2,025
Unrealized losses, continuous unrealized loss position for less than 12 months	(47)	(72)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	83	100
Fair value, continuous unrealized loss position for 12 months or more	991	1,207
Unrealized losses, continuous unrealized loss position for 12 months or more	(148)	(254)
Total unrealized losses
Total unrealized losses	(195)	(326)
Foreign government
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months		7
Fair value, continuous unrealized loss position for less than 12 months		41
Unrealized losses, continuous unrealized loss position for less than 12 months		(1)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	1	1
Fair value, continuous unrealized loss position for 12 months or more	1	1
Total unrealized losses
Total unrealized losses		(1)
RMBS
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	107	140
Fair value, continuous unrealized loss position for less than 12 months	18	152
Unrealized losses, continuous unrealized loss position for less than 12 months		(4)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	157	161
Fair value, continuous unrealized loss position for 12 months or more	697	809
Unrealized losses, continuous unrealized loss position for 12 months or more	(201)	(310)
Total unrealized losses
Total unrealized losses	(201)	(314)
CMBS
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	17	42
Fair value, continuous unrealized loss position for less than 12 months	109	361
Unrealized losses, continuous unrealized loss position for less than 12 months	(3)	(47)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	68	68
Fair value, continuous unrealized loss position for 12 months or more	567	488
Unrealized losses, continuous unrealized loss position for 12 months or more	(168)	(177)
Total unrealized losses
Total unrealized losses	(171)	(224)
ABS
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	20	32
Fair value, continuous unrealized loss position for less than 12 months	231	255
Unrealized losses, continuous unrealized loss position for less than 12 months	(19)	(13)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	89	107
Fair value, continuous unrealized loss position for 12 months or more	870	1,010
Unrealized losses, continuous unrealized loss position for 12 months or more	(191)	(268)
Total unrealized losses
Total unrealized losses	(210)	(281)
Redeemable preferred stock
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	1	1
Investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	216	351
Fair value, continuous unrealized loss position for less than 12 months	1,377	2,439
Unrealized losses, continuous unrealized loss position for less than 12 months	(43)	(111)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	271	328
Fair value, continuous unrealized loss position for 12 months or more	2,360	2,869
Unrealized losses, continuous unrealized loss position for 12 months or more	(395)	(626)
Total unrealized losses
Total unrealized losses	(438)	(737)
Below investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	61	105
Fair value, continuous unrealized loss position for less than 12 months	386	462
Unrealized losses, continuous unrealized loss position for less than 12 months	(30)	(33)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	198	206
Fair value, continuous unrealized loss position for 12 months or more	1,292	1,270
Unrealized losses, continuous unrealized loss position for 12 months or more	(394)	(490)
Total unrealized losses
Total unrealized losses	(424)	(523)
Equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	4	3
Fair value, continuous unrealized loss position for less than 12 months	17	35
Unrealized losses, continuous unrealized loss position for less than 12 months		(2)
Total unrealized losses
Gross unrealized losses on equity securities		$ (2)