Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Net income	$ 67,618	$ 45,805	$ 130,512	$ 87,867
Weighted-average shares used to calculate basic EPS (in shares)	79,479	77,923	79,361	75,383
Effect of dilutive securities:
Employee equity awards (in shares)	273	585	385	625
Weighted-average shares used to calculate diluted EPS (in shares)	79,752	78,508	79,746	76,008
Basic EPS (in dollars per share)	$ 0.85	$ 0.59	$ 1.64	$ 1.17
Diluted EPS (in dollars per share)	$ 0.85	$ 0.58	$ 1.64	$ 1.16