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		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share [Abstract]
Basic (shares)	80,790	80,949	80,729	81,003
Assumed dilution under stock plans (shares)	402	481	472	580
Diluted (shares)	81,192	81,430	81,201	81,583