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								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net income	$ 31,196	$ 35,430	$ 25,007	$ 18,224	$ 8,618	$ 20,142	$ 18,836	$ 17,273	$ 109,857	$ 64,869	$ 58,940
Weighted-average basic common shares outstanding									36,448	34,137	33,011
Stock options									2,513	2,415	2,390
Denominator for diluted earnings per share - Adjusted weighted-average shares	38,975	39,062	38,738	39,071	37,864	36,349	36,097	35,895	38,961	36,552	35,401
Basic (USD per share)		$ 0.97	$ 0.69	$ 0.50					$ 3.01	$ 1.90	$ 1.79
Diluted (USD per share)	$ 0.80	$ 0.91	$ 0.65	$ 0.47	$ 0.23	$ 0.55	$ 0.52	$ 0.48	$ 2.82	$ 1.77	$ 1.66