Marketable Securities - Summary of Marketable Securities (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 162	$ 109
Unrealized Gain (Loss)	6	1
Fair Value	168	110
U.S. government and agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	39	27
Unrealized Gain (Loss)	0	0
Fair Value	39	27
Corporate securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	33	30
Unrealized Gain (Loss)		(1)
Fair Value	33	29
Certificates of deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	24	21
Unrealized Gain (Loss)
Fair Value	24	21
Other securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	66	31
Unrealized Gain (Loss)	6	2
Fair Value	$ 72	$ 33