Significant Accounting Policies - Reconciliation of Weighted Average Number of Shares of Common Stock Outstanding In Calculating EPS (Detail) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator:
Net income	$ 36	$ 54	$ 68	$ 68	$ 20	$ 56	$ 67	$ 62	$ 226	$ 205	$ 194
Denominator:
Basic									142,721	142,854	139,462
Weighted average effect of dilutive securities:
Stock options									2,734	2,131	1,207
RSUs									345	278	161
Stock warrants											511
Weighted average shares used to compute Diluted EPS									145,800	145,263	141,341
Basic	$ 0.25	$ 0.38	$ 0.48	$ 0.48	$ 0.14	$ 0.39	$ 0.47	$ 0.44	$ 1.58	$ 1.44	$ 1.39
Diluted	$ 0.25	$ 0.37	$ 0.47	$ 0.47	$ 0.14	$ 0.38	$ 0.46	$ 0.43	$ 1.55	$ 1.41	$ 1.37