Investments (Details 10) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014 security	Dec. 31, 2013 security
Fixed income and equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	428	686
Fair value, continuous unrealized loss position for less than 12 months	$ 3,551	$ 5,988
Unrealized losses, continuous unrealized loss position for less than 12 months	(117)	(262)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	144	165
Fair value, continuous unrealized loss position for 12 months or more	1,022	1,160
Unrealized losses, continuous unrealized loss position for 12 months or more	(128)	(161)
Total unrealized losses
Total unrealized losses	(245)	(423)
Fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	400	661
Fair value, continuous unrealized loss position for less than 12 months	3,470	5,908
Unrealized losses, continuous unrealized loss position for less than 12 months	(112)	(257)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	144	165
Fair value, continuous unrealized loss position for 12 months or more	1,022	1,160
Unrealized losses, continuous unrealized loss position for 12 months or more	(128)	(161)
Total unrealized losses
Gross unrealized losses	(240)	(418)
U.S. government and agencies
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	3	4
Fair value, continuous unrealized loss position for less than 12 months	37	76
Unrealized losses, continuous unrealized loss position for less than 12 months		(2)
Total unrealized losses
Total unrealized losses		(2)
Municipal
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	37	63
Fair value, continuous unrealized loss position for less than 12 months	192	347
Unrealized losses, continuous unrealized loss position for less than 12 months	(9)	(24)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	21	21
Fair value, continuous unrealized loss position for 12 months or more	110	99
Unrealized losses, continuous unrealized loss position for 12 months or more	(27)	(38)
Total unrealized losses
Total unrealized losses	(36)	(62)
Corporate
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	309	530
Fair value, continuous unrealized loss position for less than 12 months	3,088	5,191
Unrealized losses, continuous unrealized loss position for less than 12 months	(99)	(224)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	46	48
Fair value, continuous unrealized loss position for 12 months or more	465	467
Unrealized losses, continuous unrealized loss position for 12 months or more	(62)	(71)
Total unrealized losses
Total unrealized losses	(161)	(295)
Foreign government
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	5	7
Fair value, continuous unrealized loss position for less than 12 months	55	76
Unrealized losses, continuous unrealized loss position for less than 12 months	(2)	(4)
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	14	13
Unrealized losses, continuous unrealized loss position for 12 months or more	(1)	(2)
Total unrealized losses
Total unrealized losses	(3)	(6)
ABS
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	6	17
Fair value, continuous unrealized loss position for less than 12 months	38	162
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	31	42
Fair value, continuous unrealized loss position for 12 months or more	296	400
Unrealized losses, continuous unrealized loss position for 12 months or more	(27)	(33)
Total unrealized losses
Total unrealized losses	(28)	(34)
RMBS
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	35	35
Fair value, continuous unrealized loss position for less than 12 months	38	42
Unrealized losses, continuous unrealized loss position for less than 12 months	(1)	(2)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	41	47
Fair value, continuous unrealized loss position for 12 months or more	96	129
Unrealized losses, continuous unrealized loss position for 12 months or more	(7)	(10)
Total unrealized losses
Total unrealized losses	(8)	(12)
CMBS
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	5	5
Fair value, continuous unrealized loss position for less than 12 months	22	14
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	4	6
Fair value, continuous unrealized loss position for 12 months or more	41	52
Unrealized losses, continuous unrealized loss position for 12 months or more	(4)	(7)
Total unrealized losses
Total unrealized losses	(4)	(7)
Investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	328	526
Fair value, continuous unrealized loss position for less than 12 months	3,091	5,272
Unrealized losses, continuous unrealized loss position for less than 12 months	(103)	(236)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	97	110
Fair value, continuous unrealized loss position for 12 months or more	743	834
Unrealized losses, continuous unrealized loss position for 12 months or more	(88)	(112)
Total unrealized losses
Total unrealized losses	(191)	(348)
Below investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	72	135
Fair value, continuous unrealized loss position for less than 12 months	379	636
Unrealized losses, continuous unrealized loss position for less than 12 months	(9)	(21)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more	47	55
Fair value, continuous unrealized loss position for 12 months or more	279	326
Unrealized losses, continuous unrealized loss position for 12 months or more	(40)	(49)
Total unrealized losses
Total unrealized losses	(49)	(70)
Equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	28	25
Fair value, continuous unrealized loss position for less than 12 months	81	80
Unrealized losses, continuous unrealized loss position for less than 12 months	(5)	(5)
Total unrealized losses
Gross unrealized losses on equity securities	$ (5)	$ (5)