Earnings Per Share - Computation of Basic Earnings and Diluted Earnings Per Share Data (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Net income	$ 22,264	$ 20,142	$ 58,215	$ 56,251
Weighted-average basic common shares outstanding	36,433	33,900	36,438	33,787
Stock options	2,073	2,449	2,039	2,376
Denominator for diluted earnings per share - Adjusted weighted-average shares	38,506	36,349	38,477	36,163
Basic	$ 0.61	$ 0.59	$ 1.60	$ 1.66
Diluted	$ 0.58	$ 0.55	$ 1.51	$ 1.56