Marketable Securities - Schedule of Marketable Securities (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 164	$ 164
Unrealized Gain (Loss)	5	5
Fair Value	169	169
US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	40	38
Unrealized Gain (Loss)	0	0
Fair Value	40	38
Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 42	$ 36
Unrealized Gain (Loss)
Fair Value	$ 42	$ 36
Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 22	$ 23
Unrealized Gain (Loss)
Fair Value	$ 22	$ 23
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	60	67
Unrealized Gain (Loss)	5	5
Fair Value	$ 65	$ 72