Investments (Details 11) (USD $) In Millions, unless otherwise specified	Jun. 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	380	1,554
Fair value, continuous unrealized loss position for less than 12 months	$ 2,895	$ 16,270
Unrealized losses, continuous unrealized loss position for less than 12 months	(22)	(413)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	479	319
Fair value, continuous unrealized loss position for 12 months or more	3,249	1,504
Unrealized losses, continuous unrealized loss position for 12 months or more	(156)	(194)
Total unrealized losses
Total unrealized losses	(178)	(607)
Fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	358	1,396
Fair value, continuous unrealized loss position for less than 12 months	2,724	15,288
Unrealized losses, continuous unrealized loss position for less than 12 months	(16)	(379)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	478	318
Fair value, continuous unrealized loss position for 12 months or more	3,147	1,504
Unrealized losses, continuous unrealized loss position for 12 months or more	(153)	(194)
Total unrealized losses
Total unrealized losses	(169)	(573)
U.S. government and agencies
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	24	22
Fair value, continuous unrealized loss position for less than 12 months	200	700
Unrealized losses, continuous unrealized loss position for less than 12 months	(1)	(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	(1)	(7)
Municipal
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	87	315
Fair value, continuous unrealized loss position for less than 12 months	398	2,065
Unrealized losses, continuous unrealized loss position for less than 12 months	(1)	(41)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	53	38
Fair value, continuous unrealized loss position for 12 months or more	303	208
Unrealized losses, continuous unrealized loss position for 12 months or more	(19)	(46)
Total unrealized losses
Total unrealized losses	(20)	(87)
Corporate
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	120	796
Fair value, continuous unrealized loss position for less than 12 months	1,453	10,375
Unrealized losses, continuous unrealized loss position for less than 12 months	(10)	(308)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	190	54
Fair value, continuous unrealized loss position for 12 months or more	2,121	550
Unrealized losses, continuous unrealized loss position for 12 months or more	(88)	(79)
Total unrealized losses
Total unrealized losses	(98)	(387)
Foreign government
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	2	36
Fair value, continuous unrealized loss position for less than 12 months	28	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	2	1
Fair value, continuous unrealized loss position for 12 months or more	26	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	30	85
Fair value, continuous unrealized loss position for less than 12 months	565	1,715
Unrealized losses, continuous unrealized loss position for less than 12 months	(3)	(10)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	31	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	(25)	(34)
Total unrealized losses
Total unrealized losses	(28)	(44)
Residential mortgage-backed securities ("RMBS")
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	89	134
Fair value, continuous unrealized loss position for less than 12 months	71	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	194	175
Fair value, continuous unrealized loss position for 12 months or more	239	247
Unrealized losses, continuous unrealized loss position for 12 months or more	(17)	(26)
Total unrealized losses
Total unrealized losses	(18)	(30)
Commercial mortgage-backed securities ("CMBS")
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	6	8
Fair value, continuous unrealized loss position for less than 12 months	9	22
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	5	7
Fair value, continuous unrealized loss position for 12 months or more	43	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	287	1,217
Fair value, continuous unrealized loss position for less than 12 months	2,238	14,019
Unrealized losses, continuous unrealized loss position for less than 12 months	(8)	(340)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	386	221
Fair value, continuous unrealized loss position for 12 months or more	2,620	975
Unrealized losses, continuous unrealized loss position for 12 months or more	(97)	(116)
Total unrealized losses
Total unrealized losses	(105)	(456)
Below investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	71	179
Fair value, continuous unrealized loss position for less than 12 months	486	1,269
Unrealized losses, continuous unrealized loss position for less than 12 months	(8)	(39)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	92	97
Fair value, continuous unrealized loss position for 12 months or more	527	529
Unrealized losses, continuous unrealized loss position for 12 months or more	(56)	(78)
Total unrealized losses
Total unrealized losses	(64)	(117)
Equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	22	158
Fair value, continuous unrealized loss position for less than 12 months	171	982
Unrealized losses, continuous unrealized loss position for less than 12 months	(6)	(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	102
Unrealized losses, continuous unrealized loss position for 12 months or more	(3)
Total unrealized losses
Total unrealized losses	$ (9)	$ (34)