Net Income (Loss) Per Share - Calculations of Net Income (Loss) Per Share (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
Basic:
Net income (loss)	$ (24,896)	$ (29,097)	$ (31,066)	$ (51,194)
Weighted average common shares outstanding (in shares)	20,539	20,411	20,523	20,395
Net income (loss) per share (in dollars per share)	$ (1.21)	$ (1.43)	$ (1.51)	$ (2.51)
Diluted:
Weighted average common shares outstanding	$ 20,539	$ 20,411	$ 20,523	$ 20,395
Net loss for dilutive share computation	$ 0	$ 0	$ 0	$ 0