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, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
Net income (loss)	$ 447	$ (4,532)	$ (3,779)	$ (9,550)	$ (24,989)	$ (17,414)	$ (37,773)
Weighted average common shares outstanding used to compute basic EPS					37,582	37,163	36,781
Dilutive effect of stock based awards					0	0	0
Weighted average common shares outstanding used to compute diluted EPS					37,582	37,163	36,781
Basic EPS (in dollars per share)	$ 0.01	$ (0.12)	$ (0.10)	$ (0.26)	$ (0.66)	$ (0.47)	$ (1.02)
Diluted EPS (in dollars per share)	$ 0.01	$ (0.12)	$ (0.10)	$ (0.26)	$ (0.66)	$ (0.47)	$ (1.02)
Shares of common stock excluded from the calculation of diluted net income per share because of antidilutive effect					6,500	5,300	4,800