Investments (Details 10) (USD $) In Millions, unless otherwise specified	Sep. 30, 2011	Dec. 31, 2010
Total unrealized losses
Gross unrealized losses	$ (1,807)	$ (2,431)
Gross unrealized losses on equity securities	(345)	(63)
Total unrealized losses	(2,152)	(2,494)
Fixed income and equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	3,387	2,485
Fair value, continuous unrealized loss position for less than 12 months	11,413	14,595
Unrealized losses, continuous unrealized loss position for less than 12 months	(668)	(492)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	933	1,275
Fair value, continuous unrealized loss position for 12 months or more	6,090	8,895
Unrealized losses, continuous unrealized loss position for 12 months or more	(1,484)	(2,002)
Total unrealized losses
Total unrealized losses	(2,152)
Fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	934	1,712
Fair value, continuous unrealized loss position for less than 12 months	9,346	13,985
Unrealized losses, continuous unrealized loss position for less than 12 months	(329)	(444)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	884	1,231
Fair value, continuous unrealized loss position for 12 months or more	6,070	8,804
Unrealized losses, continuous unrealized loss position for 12 months or more	(1,478)	(1,987)
Total unrealized losses
Total unrealized losses	(1,807)
U.S. government and agencies
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	6	32
Fair value, continuous unrealized loss position for less than 12 months	151	2,081
Unrealized losses, continuous unrealized loss position for less than 12 months		(51)
Total unrealized losses
Total unrealized losses		(51)
Municipal
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	173	847
Fair value, continuous unrealized loss position for less than 12 months	1,243	4,130
Unrealized losses, continuous unrealized loss position for less than 12 months	(26)	(175)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	303	411
Fair value, continuous unrealized loss position for 12 months or more	1,958	2,715
Unrealized losses, continuous unrealized loss position for 12 months or more	(236)	(471)
Total unrealized losses
Total unrealized losses	(262)	(646)
Corporate
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	509	438
Fair value, continuous unrealized loss position for less than 12 months	6,073	5,994
Unrealized losses, continuous unrealized loss position for less than 12 months	(219)	(186)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	104	150
Fair value, continuous unrealized loss position for 12 months or more	1,327	1,992
Unrealized losses, continuous unrealized loss position for 12 months or more	(231)	(235)
Total unrealized losses
Total unrealized losses	(450)	(421)
Foreign government
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	18	33
Fair value, continuous unrealized loss position for less than 12 months	346	277
Unrealized losses, continuous unrealized loss position for less than 12 months	(5)	(9)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more		1
Fair value, continuous unrealized loss position for 12 months or more		10
Unrealized losses, continuous unrealized loss position for 12 months or more		(1)
Total unrealized losses
Total unrealized losses	(5)	(10)
Residential mortgage-backed securities ("RMBS")
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	110	280
Fair value, continuous unrealized loss position for less than 12 months	284	583
Unrealized losses, continuous unrealized loss position for less than 12 months	(13)	(12)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	289	422
Fair value, continuous unrealized loss position for 12 months or more	1,193	1,939
Unrealized losses, continuous unrealized loss position for 12 months or more	(528)	(720)
Total unrealized losses
Total unrealized losses	(541)	(732)
Commercial mortgage-backed securities ("CMBS")
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	69	14
Fair value, continuous unrealized loss position for less than 12 months	566	158
Unrealized losses, continuous unrealized loss position for less than 12 months	(58)	(3)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	74	114
Fair value, continuous unrealized loss position for 12 months or more	530	835
Unrealized losses, continuous unrealized loss position for 12 months or more	(200)	(274)
Total unrealized losses
Total unrealized losses	(258)	(277)
Asset-backed securities ("ABS")
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	49	68
Fair value, continuous unrealized loss position for less than 12 months	683	762
Unrealized losses, continuous unrealized loss position for less than 12 months	(8)	(8)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	114	133
Fair value, continuous unrealized loss position for 12 months or more	1,062	1,313
Unrealized losses, continuous unrealized loss position for 12 months or more	(283)	(286)
Total unrealized losses
Total unrealized losses	(291)	(294)
Investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	633	1,607
Fair value, continuous unrealized loss position for less than 12 months	6,733	13,280
Unrealized losses, continuous unrealized loss position for less than 12 months	(182)	(408)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	567	857
Fair value, continuous unrealized loss position for 12 months or more	4,147	6,217
Unrealized losses, continuous unrealized loss position for 12 months or more	(728)	(943)
Total unrealized losses
Total unrealized losses	(910)	(1,351)
Below investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	301	105
Fair value, continuous unrealized loss position for less than 12 months	2,613	705
Unrealized losses, continuous unrealized loss position for less than 12 months	(147)	(36)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	317	374
Fair value, continuous unrealized loss position for 12 months or more	1,923	2,587
Unrealized losses, continuous unrealized loss position for 12 months or more	(750)	(1,044)
Total unrealized losses
Total unrealized losses	(897)	(1,080)
Equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	2,453	773
Fair value, continuous unrealized loss position for less than 12 months	2,067	610
Unrealized losses, continuous unrealized loss position for less than 12 months	(339)	(48)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	49	44
Fair value, continuous unrealized loss position for 12 months or more	20	91
Unrealized losses, continuous unrealized loss position for 12 months or more	$ (6)	$ (15)