Earnings Per Share - Details of Basic and Diluted Earnings Per Share (EPS) (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	$ 19,601	$ 13,504	$ 37,734	$ 30,277
Weighted average common shares outstanding used in basic EPS	43,576	43,457	43,552	43,363
Common shares issuable upon exercise of dilutive stock options and PSAs / RSUs	557	408	507	586
Weighted average common shares outstanding and common share equivalents used in diluted EPS	44,133	43,865	44,059	43,949
Earnings per share
Basic	$ 0.45	$ 0.31	$ 0.87	$ 0.70
Diluted	$ 0.44	$ 0.31	$ 0.86	$ 0.69