Earnings Per Share - Details of Basic and Diluted Earnings Per Share (EPS) (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income	$ 7,914	$ 21,554	$ 64,575
Weighted average common shares outstanding used in basic EPS	43,609	43,558	43,397
Common shares issuable upon exercise of dilutive stock options and PSAs / RSUs	830	571	545
Weighted average common shares outstanding and common share equivalents used in diluted EPS	44,439	44,129	43,942
Earnings per share
Basic	$ 0.18	$ 0.49	$ 1.49
Diluted	$ 0.18	$ 0.49	$ 1.47