Available-For-Sale Securities (Details 2) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Less than 12 months
Fair Value	$ 338	$ 109
Unrealized Losses	7	3
12 months or more
Fair Value	78	59
Unrealized Losses	3	5
Total
Fair Value	416	168
Unrealized Losses	10	8
Corporate bonds
Less than 12 months
Fair Value	174
Unrealized Losses	2
12 months or more
Fair Value	0
Unrealized Losses	0
Total
Fair Value	174
Unrealized Losses	2
Asset-backed Securities
Less than 12 months
Fair Value	4	0
Unrealized Losses	0	0
12 months or more
Fair Value	20	20
Unrealized Losses	2	3
Total
Fair Value	24	20
Unrealized Losses	2	3
U.S. governmental agency mortgage-backed securities
Less than 12 months
Fair Value	145	84
Unrealized Losses	4	1
12 months or more
Fair Value	56	15
Unrealized Losses	1	0
Total
Fair Value	201	99
Unrealized Losses	5	1
Residential
Less than 12 months
Fair Value		0
Unrealized Losses		0
12 months or more
Fair Value		14
Unrealized Losses		1
Total
Fair Value		14
Unrealized Losses		1
Large capitalization value
Less than 12 months
Fair Value	15	25
Unrealized Losses	1	2
12 months or more
Fair Value	2	10
Unrealized Losses	0	1
Total
Fair Value	17	35
Unrealized Losses	$ 1	$ 3