Net Income Per Share - Reconciliation of Shares Used in Computation of Basic and Diluted Net Income Per Share (Detail) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Basic (shares)	80,330	80,942	80,602	80,981
Assumed dilution under stock plans (shares)	407	566	450	575
Diluted (shares)	80,737	81,508	81,052	81,556