Net Income Per Common Share - Calculation of Diluted Net Income Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Numerator:
Net income	$ 25,826	$ 47,919	$ 22,708	$ 34,254
Denominator:
Weighted-average common shares, basic	79,252	76,577	78,788	76,411
Dilutive effect of common stock equivalents	5,093	3,914	2,710	4,076
Weighted-average common shares, diluted	84,345	80,491	81,498	80,487
Basic net income per common share	$ 0.33	$ 0.63	$ 0.29	$ 0.45
Diluted net income per common share	$ 0.31	$ 0.60	$ 0.28	$ 0.43