Investments and Cash - Gross Unrealized Loss by Length of Time (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013 Security	Dec. 31, 2012 Security
Less than 12 months
Fair value	$ 2,140	$ 303
Unrealized loss	(91)	(30)
12 months or more
Fair Value	237	156
Unrealized loss	(56)	(68)
Total
Fair value	2,377	459
Unrealized loss	(147)	(98)
Number of securities
Less than 12 months (in securities)	425	58
12 months or more (in securities)	33	16
Total (in securities)	458	74
Number of securities with OTTI
Less than 12 months (in securities)	13	5
12 months or more (in securities)	11	6
Total (in securities)	24	11
Obligations of state and political subdivisions
Less than 12 months
Fair value	781	79
Unrealized loss	(39)	(11)
12 months or more
Fair Value	5	0
Unrealized loss	0	0
Total
Fair value	786	79
Unrealized loss	(39)	(11)
U.S. government and agencies
Less than 12 months
Fair value	173	62
Unrealized loss	(6)	0
12 months or more
Fair Value	0	0
Unrealized loss	0	0
Total
Fair value	173	62
Unrealized loss	(6)	0
Corporate securities
Less than 12 months
Fair value	401	25
Unrealized loss	(18)	0
12 months or more
Fair Value	3	0
Unrealized loss	0	0
Total
Fair value	404	25
Unrealized loss	(18)	0
RMBS
Less than 12 months
Fair value	414	108
Unrealized loss	(21)	(19)
12 months or more
Fair Value	186	121
Unrealized loss	(51)	(58)
Total
Fair value	600	229
Unrealized loss	(72)	(77)
CMBS
Less than 12 months
Fair value	121	5
Unrealized loss	(4)	0
12 months or more
Fair Value	0	0
Unrealized loss	0	0
Total
Fair value	121	5
Unrealized loss	(4)	0
Asset-backed securities
Less than 12 months
Fair value	196	16
Unrealized loss	(2)	0
12 months or more
Fair Value	42	35
Unrealized loss	(5)	(10)
Total
Fair value	238	51
Unrealized loss	(7)	(10)
Foreign government securities
Less than 12 months
Fair value	54	8
Unrealized loss	(1)	0
12 months or more
Fair Value	1	0
Unrealized loss	0	0
Total
Fair value	55	8
Unrealized loss	$ (1)	$ 0