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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator:
Net Income	$ 20,570	$ 17,478	$ 39,507	$ 33,248
Denominator:
Weighted average basic shares (in shares)	31,443	29,545	31,425	29,608
Dilutive potential common shares (in shares)	869	606	899	582
Weighted average fully diluted shares (in shares)	32,312	30,151	32,324	30,190
Earnings per share:
Basic (in dollars per share)	$ 0.65	$ 0.59	$ 1.26	$ 1.12
Diluted (in dollars per share)	$ 0.64	$ 0.58	$ 1.22	$ 1.10
Outstanding common stock equivalents having no dilutive effect (in shares)	0	5	10	20