Investments (Details 10) (USD $) In Millions, unless otherwise specified	Jun. 30, 2011	Dec. 31, 2010
Total unrealized losses
Gross unrealized losses	$ (1,594)	$ (2,431)
Gross unrealized losses on equity securities	(80)	(63)
Total unrealized losses	(1,674)	(2,494)
Fixed income and equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	1,910	2,485
Fair value, continuous unrealized loss position for less than 12 months	9,066	14,595
Unrealized losses, continuous unrealized loss position for less than 12 months	(270)	(492)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	1,049	1,275
Fair value, continuous unrealized loss position for 12 months or more	7,029	8,895
Unrealized losses, continuous unrealized loss position for 12 months or more	(1,404)	(2,002)
Fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	1,015	1,712
Fair value, continuous unrealized loss position for less than 12 months	8,400	13,985
Unrealized losses, continuous unrealized loss position for less than 12 months	(210)	(444)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	962	1,231
Fair value, continuous unrealized loss position for 12 months or more	6,956	8,804
Unrealized losses, continuous unrealized loss position for 12 months or more	(1,384)	(1,987)
U.S. government and agencies
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	9	32
Fair value, continuous unrealized loss position for less than 12 months	198	2,081
Unrealized losses, continuous unrealized loss position for less than 12 months	(3)	(51)
Total unrealized losses
Total unrealized losses	(3)	(51)
Municipal
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	417	847
Fair value, continuous unrealized loss position for less than 12 months	1,985	4,130
Unrealized losses, continuous unrealized loss position for less than 12 months	(75)	(175)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	357	411
Fair value, continuous unrealized loss position for 12 months or more	2,222	2,715
Unrealized losses, continuous unrealized loss position for 12 months or more	(300)	(471)
Total unrealized losses
Total unrealized losses	(375)	(646)
Corporate
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	385	438
Fair value, continuous unrealized loss position for less than 12 months	4,980	5,994
Unrealized losses, continuous unrealized loss position for less than 12 months	(95)	(186)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	113	150
Fair value, continuous unrealized loss position for 12 months or more	1,552	1,992
Unrealized losses, continuous unrealized loss position for 12 months or more	(160)	(235)
Total unrealized losses
Total unrealized losses	(255)	(421)
Foreign government
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	25	33
Fair value, continuous unrealized loss position for less than 12 months	114	277
Unrealized losses, continuous unrealized loss position for less than 12 months	(4)	(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	(4)	(10)
Residential mortgage-backed securities ("RMBS")
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	120	280
Fair value, continuous unrealized loss position for less than 12 months	368	583
Unrealized losses, continuous unrealized loss position for less than 12 months	(12)	(12)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	296	422
Fair value, continuous unrealized loss position for 12 months or more	1,338	1,939
Unrealized losses, continuous unrealized loss position for 12 months or more	(557)	(720)
Total unrealized losses
Total unrealized losses	(569)	(732)
Commercial mortgage-backed securities ("CMBS")
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	29	14
Fair value, continuous unrealized loss position for less than 12 months	314	158
Unrealized losses, continuous unrealized loss position for less than 12 months	(16)	(3)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	75	114
Fair value, continuous unrealized loss position for 12 months or more	609	835
Unrealized losses, continuous unrealized loss position for 12 months or more	(138)	(274)
Total unrealized losses
Total unrealized losses	(154)	(277)
Asset-backed securities ("ABS")
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	30	68
Fair value, continuous unrealized loss position for less than 12 months	441	762
Unrealized losses, continuous unrealized loss position for less than 12 months	(5)	(8)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	121	133
Fair value, continuous unrealized loss position for 12 months or more	1,235	1,313
Unrealized losses, continuous unrealized loss position for 12 months or more	(229)	(286)
Total unrealized losses
Total unrealized losses	(234)	(294)
Investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	836	1,607
Fair value, continuous unrealized loss position for less than 12 months	6,786	13,280
Unrealized losses, continuous unrealized loss position for less than 12 months	(156)	(408)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	618	857
Fair value, continuous unrealized loss position for 12 months or more	4,665	6,217
Unrealized losses, continuous unrealized loss position for 12 months or more	(607)	(943)
Total unrealized losses
Total unrealized losses	(763)	(1,351)
Below investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	179	105
Fair value, continuous unrealized loss position for less than 12 months	1,614	705
Unrealized losses, continuous unrealized loss position for less than 12 months	(54)	(36)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	344	374
Fair value, continuous unrealized loss position for 12 months or more	2,291	2,587
Unrealized losses, continuous unrealized loss position for 12 months or more	(777)	(1,044)
Total unrealized losses
Total unrealized losses	(831)	(1,080)
Equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	895	773
Fair value, continuous unrealized loss position for less than 12 months	666	610
Unrealized losses, continuous unrealized loss position for less than 12 months	(60)	(48)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	87	44
Fair value, continuous unrealized loss position for 12 months or more	73	91
Unrealized losses, continuous unrealized loss position for 12 months or more	$ (20)	$ (15)