Investments and Cash (Details 4) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012 Security	Dec. 31, 2011 Security
Less than 12 months
Fair value	$ 303	$ 432
Unrealized loss	(30)	(76)
12 months or more
Fair Value	156	86
Unrealized loss	(68)	(42)
Total
Fair value	459	518
Unrealized loss	(98)	(118)
Number of securities
Less than 12 months (in securities)	58	56
12 months or more (in securities)	16	20
Total (in securities)	74	76
Number of securities with OTTI
Less than 12 months (in securities)	5	6
12 months or more (in securities)	6	4
Total (in securities)	11	10
Number of securities with unrealized losses greater than 10% of book value for 12 months or more	9
Threshold for measuring unrealized losses for securities as a percent of book value	10.00%
Total unrealized losses for securities having losses greater than 10% of book value for 12 months or more	67
U.S. government and agencies
Less than 12 months
Fair value	62	4
Unrealized loss	0	0
12 months or more
Fair Value	0	0
Unrealized loss	0	0
Total
Fair value	62	4
Unrealized loss	0	0
Obligations of state and political subdivisions
Less than 12 months
Fair value	79	17
Unrealized loss	(11)	0
12 months or more
Fair Value	0	21
Unrealized loss	0	(1)
Total
Fair value	79	38
Unrealized loss	(11)	(1)
Corporate securities
Less than 12 months
Fair value	25	80
Unrealized loss	0	(2)
12 months or more
Fair Value	0	3
Unrealized loss	0	0
Total
Fair value	25	83
Unrealized loss	0	(2)
RMBS
Less than 12 months
Fair value	108	187
Unrealized loss	(19)	(68)
12 months or more
Fair Value	121	36
Unrealized loss	(58)	(22)
Total
Fair value	229	223
Unrealized loss	(77)	(90)
CMBS
Less than 12 months
Fair value	5	3
Unrealized loss	0	0
12 months or more
Fair Value	0	0
Unrealized loss	0	0
Total
Fair value	5	3
Unrealized loss	0	0
Asset-backed securities
Less than 12 months
Fair value	16	0
Unrealized loss	0	0
12 months or more
Fair Value	35	26
Unrealized loss	(10)	(19)
Total
Fair value	51	26
Unrealized loss	(10)	(19)
Foreign government securities
Less than 12 months
Fair value	8	141
Unrealized loss	0	(6)
12 months or more
Fair Value	0	0
Unrealized loss	0	0
Total
Fair value	8	141
Unrealized loss	$ 0	$ (6)