Marketable Securities - Summary of Marketable Securities (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 141	$ 109
Unrealized Gain (Loss)	3	1
Fair Value	144	110
U.S. government and agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	38	27
Unrealized Gain (Loss)	0	0
Fair Value	38	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	22	21
Unrealized Gain (Loss)
Fair Value	22	21
Other securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	48	31
Unrealized Gain (Loss)	3	2
Fair Value	$ 51	$ 33