Investments-Portfolio Monitoring (Details 11) $ in Millions	Jun. 30, 2016 USD ($) security	Dec. 31, 2015 USD ($) security
Fixed income and equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	563	1,385
Fair value, continuous unrealized loss position for less than 12 months	$ 1,764	$ 7,310
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (100)	$ (346)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	275	172
Fair value, continuous unrealized loss position for 12 months or more	$ 1,196	$ 858
Unrealized losses, continuous unrealized loss position for 12 months or more	(152)	(176)
Total unrealized losses
Total unrealized losses	$ (252)	$ (522)
Fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	315	1,106
Fair value, continuous unrealized loss position for less than 12 months	$ 1,401	$ 6,767
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (52)	$ (297)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	204	140
Fair value, continuous unrealized loss position for 12 months or more	$ 1,110	$ 802
Unrealized losses, continuous unrealized loss position for 12 months or more	(135)	(165)
Total unrealized losses
Gross unrealized losses	$ (187)	$ (462)
U.S. government and agencies
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	5	6
Fair value, continuous unrealized loss position for less than 12 months	$ 60	$ 91
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 (in Security) | security	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	$ 0	$ 0
Municipal
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	2	15
Fair value, continuous unrealized loss position for less than 12 months	$ 1	$ 125
Unrealized losses, continuous unrealized loss position for less than 12 months	$ 0	$ (3)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	3	5
Fair value, continuous unrealized loss position for 12 months or more	$ 17	$ 25
Unrealized losses, continuous unrealized loss position for 12 months or more	(6)	(9)
Total unrealized losses
Total unrealized losses	$ (6)	$ (12)
Corporate
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	220	953
Fair value, continuous unrealized loss position for less than 12 months	$ 1,107	$ 5,315
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (44)	$ (281)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	143	78
Fair value, continuous unrealized loss position for 12 months or more	$ 912	$ 568
Unrealized losses, continuous unrealized loss position for 12 months or more	(110)	(133)
Total unrealized losses
Total unrealized losses	$ (154)	$ (414)
Foreign government
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security		1
Fair value, continuous unrealized loss position for less than 12 months		$ 2
Unrealized losses, continuous unrealized loss position for less than 12 months		$ 0
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security		0
Fair value, continuous unrealized loss position for 12 months or more		$ 0
Unrealized losses, continuous unrealized loss position for 12 months or more		0
Total unrealized losses
Total unrealized losses		$ 0
ABS
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	24	81
Fair value, continuous unrealized loss position for less than 12 months	$ 144	$ 1,152
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (2)	$ (11)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	17	16
Fair value, continuous unrealized loss position for 12 months or more	$ 136	$ 154
Unrealized losses, continuous unrealized loss position for 12 months or more	(14)	(17)
Total unrealized losses
Total unrealized losses	$ (16)	$ (28)
RMBS
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	50	38
Fair value, continuous unrealized loss position for less than 12 months	$ 11	$ 7
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 (in Security) | security	40	40
Fair value, continuous unrealized loss position for 12 months or more	$ 43	$ 53
Unrealized losses, continuous unrealized loss position for 12 months or more	(4)	(4)
Total unrealized losses
Total unrealized losses	$ (4)	$ (4)
CMBS
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	14	12
Fair value, continuous unrealized loss position for less than 12 months	$ 78	$ 75
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (6)	$ (2)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	1	1
Fair value, continuous unrealized loss position for 12 months or more	$ 2	$ 2
Unrealized losses, continuous unrealized loss position for 12 months or more	(1)	(2)
Total unrealized losses
Total unrealized losses	$ (7)	$ (4)
Equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	248	279
Fair value, continuous unrealized loss position for less than 12 months	$ 363	$ 543
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (48)	$ (49)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	71	32
Fair value, continuous unrealized loss position for 12 months or more	$ 86	$ 56
Unrealized losses, continuous unrealized loss position for 12 months or more	(17)	(11)
Total unrealized losses
Gross unrealized losses on equity securities	$ (65)	$ (60)
Investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	137	780
Fair value, continuous unrealized loss position for less than 12 months	$ 632	$ 5,429
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (13)	$ (175)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	99	82
Fair value, continuous unrealized loss position for 12 months or more	$ 605	$ 503
Unrealized losses, continuous unrealized loss position for 12 months or more	(74)	(90)
Total unrealized losses
Total unrealized losses	$ (87)	$ (265)
Below investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	178	326
Fair value, continuous unrealized loss position for less than 12 months	$ 769	$ 1,338
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (39)	$ (122)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	105	58
Fair value, continuous unrealized loss position for 12 months or more	$ 505	$ 299
Unrealized losses, continuous unrealized loss position for 12 months or more	(61)	(75)
Total unrealized losses
Total unrealized losses	$ (100)	$ (197)