Available-For-Sale Securities (Details 2) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Less than 12 months
Fair Value	$ 282	$ 305
Unrealized Losses	4	6
12 months or more
Fair Value	124	86
Unrealized Losses	5	3
Total
Fair Value	406	391
Unrealized Losses	9	9
Corporate bonds
Less than 12 months
Fair Value	159	159
Unrealized Losses	1	2
12 months or more
Fair Value	1	1
Unrealized Losses	0	0
Total
Fair Value	160	160
Unrealized Losses	1	2
Asset-backed Securities
Less than 12 months
Fair Value	5	6
Unrealized Losses	0	0
12 months or more
Fair Value	17	20
Unrealized Losses	1	1
Total
Fair Value	22	26
Unrealized Losses	1	1
U.S. governmental agency mortgage-backed securities
Less than 12 months
Fair Value	98	140
Unrealized Losses	2	4
12 months or more
Fair Value	105	65
Unrealized Losses	4	2
Total
Fair Value	203	205
Unrealized Losses	6	6
Large capitalization value
Less than 12 months
Fair Value	20
Unrealized Losses	1
12 months or more
Fair Value	1
Unrealized Losses	0
Total
Fair Value	21
Unrealized Losses	$ 1