Investments-Portfolio Monitoring (Details 11) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015 security	Dec. 31, 2014 security
Fixed income and equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	544	639
Fair value, continuous unrealized loss position for less than 12 months	$ 2,094	$ 2,402
Unrealized losses, continuous unrealized loss position for less than 12 months	(81)	(85)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security)	122	174
Fair value, continuous unrealized loss position for 12 months or more	842	1,265
Unrealized losses, continuous unrealized loss position for 12 months or more	(104)	(120)
Total unrealized losses
Total unrealized losses	(185)	(205)
Fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	299	345
Fair value, continuous unrealized loss position for less than 12 months	1,800	2,075
Unrealized losses, continuous unrealized loss position for less than 12 months	(59)	(72)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security)	121	173
Fair value, continuous unrealized loss position for 12 months or more	836	1,259
Unrealized losses, continuous unrealized loss position for 12 months or more	(103)	(119)
Total unrealized losses
Gross unrealized losses	(162)	(191)
U.S. government and agencies
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months		1
Fair value, continuous unrealized loss position for less than 12 months		1
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)		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
Municipal
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	20	17
Fair value, continuous unrealized loss position for less than 12 months	39	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)	5	10
Fair value, continuous unrealized loss position for 12 months or more	33	47
Unrealized losses, continuous unrealized loss position for 12 months or more	(11)	(13)
Total unrealized losses
Total unrealized losses	(12)	(14)
Corporate
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	231	281
Fair value, continuous unrealized loss position for less than 12 months	1,449	1,780
Unrealized losses, continuous unrealized loss position for less than 12 months	(55)	(69)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security)	52	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	(69)	(81)
Total unrealized losses
Total unrealized losses	(124)	(150)
Foreign government
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	1	0
Fair value, continuous unrealized loss position for less than 12 months	7	0
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)	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	0	0
ABS
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	25	19
Fair value, continuous unrealized loss position for less than 12 months	292	168
Unrealized losses, continuous unrealized loss position for less than 12 months	(3)	(2)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security)	20	23
Fair value, continuous unrealized loss position for 12 months or more	174	217
Unrealized losses, continuous unrealized loss position for 12 months or more	(18)	(19)
Total unrealized losses
Total unrealized losses	(21)	(21)
RMBS
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	18	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)	42	45
Fair value, continuous unrealized loss position for 12 months or more	65	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	4	8
Fair value, continuous unrealized loss position for less than 12 months	11	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)	2	3
Fair value, continuous unrealized loss position for 12 months or more	13	32
Unrealized losses, continuous unrealized loss position for 12 months or more	(1)	(2)
Total unrealized losses
Total unrealized losses	(1)	(2)
Investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	152	167
Fair value, continuous unrealized loss position for less than 12 months	1,128	1,275
Unrealized losses, continuous unrealized loss position for less than 12 months	(26)	(28)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security)	82	127
Fair value, continuous unrealized loss position for 12 months or more	604	989
Unrealized losses, continuous unrealized loss position for 12 months or more	(65)	(79)
Total unrealized losses
Total unrealized losses	(91)	(107)
Below investment grade fixed income securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	147	178
Fair value, continuous unrealized loss position for less than 12 months	672	800
Unrealized losses, continuous unrealized loss position for less than 12 months	(33)	(44)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security)	39	46
Fair value, continuous unrealized loss position for 12 months or more	232	270
Unrealized losses, continuous unrealized loss position for 12 months or more	(38)	(40)
Total unrealized losses
Total unrealized losses	(71)	(84)
Equity securities
Less than 12 months
Number of issues, continuous unrealized loss position for less than 12 months	245	294
Fair value, continuous unrealized loss position for less than 12 months	294	327
Unrealized losses, continuous unrealized loss position for less than 12 months	(22)	(13)
12 months or more
Number of issues, continuous unrealized loss position for 12 months or more (in Security)	1	1
Fair value, continuous unrealized loss position for 12 months or more	6	6
Unrealized losses, continuous unrealized loss position for 12 months or more	(1)	(1)
Total unrealized losses
Gross unrealized losses on equity securities	$ (23)	$ (14)