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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Net income (loss)	$ (7,399)	$ (5,714)	$ (1,683)	$ 5,889
Weighted average common shares outstanding used in basic EPS	43,770	43,604	43,735	43,593
Common shares issuable upon exercise of dilutive stock options and PSAs / RSUs				856
Weighted average common shares outstanding and common share equivalents used in diluted EPS	43,770	43,604	43,735	44,449
Earnings (loss) per share
Basic	$ (0.17)	$ (0.13)	$ (0.04)	$ 0.14
Diluted	$ (0.17)	$ (0.13)	$ (0.04)	$ 0.13