Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Numerator:
Net Income	$ 18,937	$ 15,770
Denominator:
Weighted average basic shares (in shares)	31,407	29,671
Dilutive potential common shares (in shares)	942	558
Weighted average fully diluted shares (in shares)	32,349	30,229
Earnings per share:
Basic (in dollars per share)	$ 0.60	$ 0.53
Diluted (in dollars per share)	$ 0.59	$ 0.52
Outstanding common stock equivalents having no dilutive effect (in shares)	22	42