Earnings Per Share - Reconciliation of Weighted Average Number of Shares of Common Stock Outstanding (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Numerator:
Net income	$ 68	$ 62
Denominator:
Weighted average shares used to compute Basic EPS	142,399	143,063
Weighted average effect of dilutive securities:
Stock options	2,884	1,401
RSUs	382	191
Weighted average shares used to compute Diluted EPS	145,665	144,655
Basic EPS	$ 0.48	$ 0.44
Diluted EPS	$ 0.47	$ 0.43