Investments-Portfolio Monitoring (Details 11) $ in Millions	Jun. 30, 2015 USD ($) security	Dec. 31, 2014 USD ($) security
Fixed income and equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	1,021	639
Fair value, continuous unrealized loss position for less than 12 months	$ 4,986	$ 2,402
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (168)	$ (85)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	116	174
Fair value, continuous unrealized loss position for 12 months or more	$ 737	$ 1,265
Unrealized losses, continuous unrealized loss position for 12 months or more	(109)	(120)
Total unrealized losses
Total unrealized losses	$ (277)	$ (205)
Fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	716	345
Fair value, continuous unrealized loss position for less than 12 months	$ 4,663	$ 2,075
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (139)	$ (72)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	116	173
Fair value, continuous unrealized loss position for 12 months or more	$ 737	$ 1,259
Unrealized losses, continuous unrealized loss position for 12 months or more	(109)	(119)
Total unrealized losses
Gross unrealized losses	$ (248)	$ (191)
U.S. government and agencies
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	2	1
Fair value, continuous unrealized loss position for less than 12 months	$ 175	$ 1
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	43	17
Fair value, continuous unrealized loss position for less than 12 months	$ 173	$ 90
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (8)	$ (1)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	5	10
Fair value, continuous unrealized loss position for 12 months or more	$ 32	$ 47
Unrealized losses, continuous unrealized loss position for 12 months or more	(12)	(13)
Total unrealized losses
Total unrealized losses	$ (20)	$ (14)
Corporate
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	610	281
Fair value, continuous unrealized loss position for less than 12 months	$ 3,877	$ 1,780
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (126)	$ (69)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	48	91
Fair value, continuous unrealized loss position for 12 months or more	$ 466	$ 875
Unrealized losses, continuous unrealized loss position for 12 months or more	(75)	(81)
Total unrealized losses
Total unrealized losses	$ (201)	$ (150)
Foreign government
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	3	0
Fair value, continuous unrealized loss position for less than 12 months	$ 16	$ 0
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (1)	$ 0
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	0	1
Fair value, continuous unrealized loss position for 12 months or more	$ 0	$ 15
Unrealized losses, continuous unrealized loss position for 12 months or more	0	0
Total unrealized losses
Total unrealized losses	$ (1)	$ 0
ABS
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	29	19
Fair value, continuous unrealized loss position for less than 12 months	$ 390	$ 168
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (4)	$ (2)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	20	23
Fair value, continuous unrealized loss position for 12 months or more	$ 175	$ 217
Unrealized losses, continuous unrealized loss position for 12 months or more	(16)	(19)
Total unrealized losses
Total unrealized losses	$ (20)	$ (21)
RMBS
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	22	19
Fair value, continuous unrealized loss position for less than 12 months	$ 2	$ 3
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	42	45
Fair value, continuous unrealized loss position for 12 months or more	$ 61	$ 73
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	7	8
Fair value, continuous unrealized loss position for less than 12 months	$ 30	$ 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 (in Security) | security	1	3
Fair value, continuous unrealized loss position for 12 months or more	$ 3	$ 32
Unrealized losses, continuous unrealized loss position for 12 months or more	(2)	(2)
Total unrealized losses
Total unrealized losses	$ (2)	$ (2)
Equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	305	294
Fair value, continuous unrealized loss position for less than 12 months	$ 323	$ 327
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (29)	$ (13)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	0	1
Fair value, continuous unrealized loss position for 12 months or more	$ 0	$ 6
Unrealized losses, continuous unrealized loss position for 12 months or more	0	(1)
Total unrealized losses
Gross unrealized losses on equity securities	$ (29)	$ (14)
Investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	447	167
Fair value, continuous unrealized loss position for less than 12 months	$ 3,408	$ 1,275
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (84)	$ (28)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	76	127
Fair value, continuous unrealized loss position for 12 months or more	$ 511	$ 989
Unrealized losses, continuous unrealized loss position for 12 months or more	(66)	(79)
Total unrealized losses
Total unrealized losses	$ (150)	$ (107)
Below investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	269	178
Fair value, continuous unrealized loss position for less than 12 months	$ 1,255	$ 800
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (55)	$ (44)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	40	46
Fair value, continuous unrealized loss position for 12 months or more	$ 226	$ 270
Unrealized losses, continuous unrealized loss position for 12 months or more	(43)	(40)
Total unrealized losses
Total unrealized losses	$ (98)	$ (84)