Earnings (Loss) Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income (loss)	$ 447	$ (4,532)	$ (3,779)	$ (9,550)	$ (10,203)	$ (3,334)	$ (8,826)	$ (15,410)	$ (17,414)	$ (37,773)	$ (83,462)
Weighted average common shares outstanding used to compute basic EPS									37,163	36,781	36,165
Dilutive effect of stock based awards									0	0	0
Weighted average common shares outstanding used to compute diluted EPS									37,163	36,781	36,165
Basic EPS (in dollars per share)	$ 0.01	$ (0.12)	$ (0.10)	$ (0.26)	$ (0.28)	$ (0.09)	$ (0.24)	$ (0.42)	$ (0.47)	$ (1.02)	$ (2.31)
Diluted EPS (in dollars per share)	$ 0.01	$ (0.12)	$ (0.10)	$ (0.26)	$ (0.28)	$ (0.09)	$ (0.24)	$ (0.42)	$ (0.47)	$ (1.02)	$ (2.31)
Shares of common stock excluded from the calculation of diluted net income per share because of antidilutive effect									5,300	4,800	5,700