Investments (Details 11) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014 contract	Dec. 31, 2013 contract
Fixed income and equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	1,155	1,554
Fair value, continuous unrealized loss position for less than 12 months	$ 12,228	$ 16,270
Unrealized losses, continuous unrealized loss position for less than 12 months	(128)	(413)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	438	319
Fair value, continuous unrealized loss position for 12 months or more	2,671	1,504
Unrealized losses, continuous unrealized loss position for 12 months or more	(156)	(194)
Total unrealized losses
Total unrealized losses	(284)	(607)
Fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	802	1,396
Fair value, continuous unrealized loss position for less than 12 months	11,296	15,288
Unrealized losses, continuous unrealized loss position for less than 12 months	(110)	(379)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	437	318
Fair value, continuous unrealized loss position for 12 months or more	2,659	1,504
Unrealized losses, continuous unrealized loss position for 12 months or more	(155)	(194)
Total unrealized losses
Total unrealized losses	(265)	(573)
U.S. government and agencies
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	18	22
Fair value, continuous unrealized loss position for less than 12 months	1,761	700
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	3
Fair value, continuous unrealized loss position for 12 months or more	22
Total unrealized losses
Total unrealized losses	(4)	(7)
Municipal
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	86	315
Fair value, continuous unrealized loss position for less than 12 months	359	2,065
Unrealized losses, continuous unrealized loss position for less than 12 months	(7)	(41)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	38	38
Fair value, continuous unrealized loss position for 12 months or more	227	208
Unrealized losses, continuous unrealized loss position for 12 months or more	(16)	(46)
Total unrealized losses
Total unrealized losses	(23)	(87)
Corporate
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	535	796
Fair value, continuous unrealized loss position for less than 12 months	6,974	10,375
Unrealized losses, continuous unrealized loss position for less than 12 months	(89)	(308)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	163	54
Fair value, continuous unrealized loss position for 12 months or more	1,767	550
Unrealized losses, continuous unrealized loss position for 12 months or more	(99)	(79)
Total unrealized losses
Total unrealized losses	(188)	(387)
Foreign government
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	7	36
Fair value, continuous unrealized loss position for less than 12 months	90	262
Unrealized losses, continuous unrealized loss position for less than 12 months		(9)
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	19	18
Unrealized losses, continuous unrealized loss position for 12 months or more	(1)	(2)
Total unrealized losses
Total unrealized losses	(1)	(11)
Asset-backed securities ("ABS")
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	83	85
Fair value, continuous unrealized loss position for less than 12 months	2,055	1,715
Unrealized losses, continuous unrealized loss position for less than 12 months	(9)	(10)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	28	43
Fair value, continuous unrealized loss position for 12 months or more	393	429
Unrealized losses, continuous unrealized loss position for 12 months or more	(23)	(34)
Total unrealized losses
Total unrealized losses	(32)	(44)
Residential mortgage-backed securities ("RMBS")
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	68	134
Fair value, continuous unrealized loss position for less than 12 months	53	149
Unrealized losses, continuous unrealized loss position for less than 12 months	(1)	(4)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	200	175
Fair value, continuous unrealized loss position for 12 months or more	189	247
Unrealized losses, continuous unrealized loss position for 12 months or more	(13)	(26)
Total unrealized losses
Total unrealized losses	(14)	(30)
Commercial mortgage-backed securities ("CMBS")
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	5	8
Fair value, continuous unrealized loss position for less than 12 months	4	22
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	4	7
Fair value, continuous unrealized loss position for 12 months or more	42	52
Unrealized losses, continuous unrealized loss position for 12 months or more	(3)	(7)
Total unrealized losses
Total unrealized losses	(3)	(7)
Investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	532	1,217
Fair value, continuous unrealized loss position for less than 12 months	9,199	14,019
Unrealized losses, continuous unrealized loss position for less than 12 months	(50)	(340)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	353	221
Fair value, continuous unrealized loss position for 12 months or more	2,219	975
Unrealized losses, continuous unrealized loss position for 12 months or more	(102)	(116)
Total unrealized losses
Total unrealized losses	(152)	(456)
Below investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	270	179
Fair value, continuous unrealized loss position for less than 12 months	2,097	1,269
Unrealized losses, continuous unrealized loss position for less than 12 months	(60)	(39)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	84	97
Fair value, continuous unrealized loss position for 12 months or more	440	529
Unrealized losses, continuous unrealized loss position for 12 months or more	(53)	(78)
Total unrealized losses
Total unrealized losses	(113)	(117)
Equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	353	158
Fair value, continuous unrealized loss position for less than 12 months	932	982
Unrealized losses, continuous unrealized loss position for less than 12 months	(18)	(34)
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	12
Unrealized losses, continuous unrealized loss position for 12 months or more	(1)
Total unrealized losses
Total unrealized losses	$ (19)	$ (34)