Investments-Portfolio Monitoring (Details 11) $ in Millions	Sep. 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	1,203	639
Fair value, continuous unrealized loss position for less than 12 months	$ 5,204	$ 2,402
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (328)	$ (85)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	126	174
Fair value, continuous unrealized loss position for 12 months or more	$ 822	$ 1,265
Unrealized losses, continuous unrealized loss position for 12 months or more	(128)	(120)
Total unrealized losses
Total unrealized losses	$ (456)	$ (205)
Fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	784	345
Fair value, continuous unrealized loss position for less than 12 months	$ 4,462	$ 2,075
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (254)	$ (72)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	126	173
Fair value, continuous unrealized loss position for 12 months or more	$ 822	$ 1,259
Unrealized losses, continuous unrealized loss position for 12 months or more	(128)	(119)
Total unrealized losses
Gross unrealized losses	$ (382)	$ (191)
U.S. government and agencies
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	1	1
Fair value, continuous unrealized loss position for less than 12 months	$ 5	$ 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	21	17
Fair value, continuous unrealized loss position for less than 12 months	$ 56	$ 90
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 (in Security) | security	5	10
Fair value, continuous unrealized loss position for 12 months or more	$ 24	$ 47
Unrealized losses, continuous unrealized loss position for 12 months or more	(8)	(13)
Total unrealized losses
Total unrealized losses	$ (9)	$ (14)
Corporate
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	686	281
Fair value, continuous unrealized loss position for less than 12 months	$ 3,948	$ 1,780
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (244)	$ (69)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	60	91
Fair value, continuous unrealized loss position for 12 months or more	$ 551	$ 875
Unrealized losses, continuous unrealized loss position for 12 months or more	(96)	(81)
Total unrealized losses
Total unrealized losses	$ (340)	$ (150)
Foreign government
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	2	0
Fair value, continuous unrealized loss position for less than 12 months	$ 32	$ 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	37	19
Fair value, continuous unrealized loss position for less than 12 months	$ 387	$ 168
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (8)	$ (2)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	19	23
Fair value, continuous unrealized loss position for 12 months or more	$ 186	$ 217
Unrealized losses, continuous unrealized loss position for 12 months or more	(17)	(19)
Total unrealized losses
Total unrealized losses	$ (25)	$ (21)
RMBS
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	31	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	40	45
Fair value, continuous unrealized loss position for 12 months or more	$ 57	$ 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	6	8
Fair value, continuous unrealized loss position for less than 12 months	$ 32	$ 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	2	3
Fair value, continuous unrealized loss position for 12 months or more	$ 4	$ 32
Unrealized losses, continuous unrealized loss position for 12 months or more	(3)	(2)
Total unrealized losses
Total unrealized losses	$ (3)	$ (2)
Equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	419	294
Fair value, continuous unrealized loss position for less than 12 months	$ 742	$ 327
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (74)	$ (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	$ (74)	$ (14)
Investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	422	167
Fair value, continuous unrealized loss position for less than 12 months	$ 2,931	$ 1,275
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (114)	$ (28)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	77	127
Fair value, continuous unrealized loss position for 12 months or more	$ 550	$ 989
Unrealized losses, continuous unrealized loss position for 12 months or more	(73)	(79)
Total unrealized losses
Total unrealized losses	$ (187)	$ (107)
Below investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months | security	362	178
Fair value, continuous unrealized loss position for less than 12 months	$ 1,531	$ 800
Unrealized losses, continuous unrealized loss position for less than 12 months	$ (140)	$ (44)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security) | security	49	46
Fair value, continuous unrealized loss position for 12 months or more	$ 272	$ 270
Unrealized losses, continuous unrealized loss position for 12 months or more	(55)	(40)
Total unrealized losses
Total unrealized losses	$ (195)	$ (84)