Investments (Details 11) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015 contract	Dec. 31, 2014 contract
Fixed income and equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	907	1,273
Fair value, continuous unrealized loss position for less than 12 months	$ 6,551	$ 12,774
Unrealized losses, continuous unrealized loss position for less than 12 months	(170)	(224)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	284	357
Fair value, continuous unrealized loss position for 12 months or more	1,215	1,863
Unrealized losses, continuous unrealized loss position for 12 months or more	(121)	(145)
Total unrealized losses
Total unrealized losses	(291)	(369)
Fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	697	1,015
Fair value, continuous unrealized loss position for less than 12 months	5,764	11,908
Unrealized losses, continuous unrealized loss position for less than 12 months	(118)	(171)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	283	356
Fair value, continuous unrealized loss position for 12 months or more	1,204	1,852
Unrealized losses, continuous unrealized loss position for 12 months or more	(119)	(143)
Total unrealized losses
Total unrealized losses	(237)	(314)
U.S. government and agencies
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	7	21
Fair value, continuous unrealized loss position for less than 12 months	657	1,501
Unrealized losses, continuous unrealized loss position for less than 12 months	(3)	(3)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	0	0
Fair value, continuous unrealized loss position for 12 months or more	0	0
Unrealized losses, continuous unrealized loss position for 12 months or more	0	0
Total unrealized losses
Total unrealized losses	(3)	(3)
Municipal
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	216	252
Fair value, continuous unrealized loss position for less than 12 months	701	1,008
Unrealized losses, continuous unrealized loss position for less than 12 months	(8)	(9)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	9	19
Fair value, continuous unrealized loss position for 12 months or more	61	116
Unrealized losses, continuous unrealized loss position for 12 months or more	(13)	(16)
Total unrealized losses
Total unrealized losses	(21)	(25)
Corporate
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	342	576
Fair value, continuous unrealized loss position for less than 12 months	3,596	7,545
Unrealized losses, continuous unrealized loss position for less than 12 months	(99)	(147)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	69	119
Fair value, continuous unrealized loss position for 12 months or more	675	1,214
Unrealized losses, continuous unrealized loss position for 12 months or more	(75)	(93)
Total unrealized losses
Total unrealized losses	(174)	(240)
Foreign government
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	4	2
Fair value, continuous unrealized loss position for less than 12 months	28	13
Unrealized losses, continuous unrealized loss position for less than 12 months	0	0
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	0	1
Fair value, continuous unrealized loss position for 12 months or more	0	19
Unrealized losses, continuous unrealized loss position for 12 months or more	0	0
Total unrealized losses
Total unrealized losses	0	0
Asset-backed securities (“ABS”)
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	47	81
Fair value, continuous unrealized loss position for less than 12 months	753	1,738
Unrealized losses, continuous unrealized loss position for less than 12 months	(7)	(11)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	24	26
Fair value, continuous unrealized loss position for 12 months or more	301	315
Unrealized losses, continuous unrealized loss position for 12 months or more	(19)	(20)
Total unrealized losses
Total unrealized losses	(26)	(31)
Residential mortgage-backed securities (“RMBS”)
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	77	75
Fair value, continuous unrealized loss position for less than 12 months	18	70
Unrealized losses, continuous unrealized loss position for less than 12 months	(1)	(1)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	179	188
Fair value, continuous unrealized loss position for 12 months or more	154	156
Unrealized losses, continuous unrealized loss position for 12 months or more	(11)	(12)
Total unrealized losses
Total unrealized losses	(12)	(13)
Commercial mortgage-backed securities (“CMBS”)
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	4	8
Fair value, continuous unrealized loss position for less than 12 months	11	33
Unrealized losses, continuous unrealized loss position for less than 12 months	0	0
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	2	3
Fair value, continuous unrealized loss position for 12 months or more	13	32
Unrealized losses, continuous unrealized loss position for 12 months or more	(1)	(2)
Total unrealized losses
Total unrealized losses	(1)	(2)
Investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	500	754
Fair value, continuous unrealized loss position for less than 12 months	4,171	9,951
Unrealized losses, continuous unrealized loss position for less than 12 months	(42)	(71)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	216	281
Fair value, continuous unrealized loss position for 12 months or more	837	1,444
Unrealized losses, continuous unrealized loss position for 12 months or more	(68)	(87)
Total unrealized losses
Total unrealized losses	(110)	(158)
Below investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	197	261
Fair value, continuous unrealized loss position for less than 12 months	1,593	1,957
Unrealized losses, continuous unrealized loss position for less than 12 months	(76)	(100)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	67	75
Fair value, continuous unrealized loss position for 12 months or more	367	408
Unrealized losses, continuous unrealized loss position for 12 months or more	(51)	(56)
Total unrealized losses
Total unrealized losses	(127)	(156)
Equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	210	258
Fair value, continuous unrealized loss position for less than 12 months	787	866
Unrealized losses, continuous unrealized loss position for less than 12 months	(52)	(53)
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	11	11
Unrealized losses, continuous unrealized loss position for 12 months or more	(2)	(2)
Total unrealized losses
Total unrealized losses	$ (54)	$ (55)