Summary of Significant Accounting Policies - Basic and Diluted Net (Loss) Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator
Net (loss) income from continuing operations	$ (126,022)	$ (68,686)	$ (41,704)
Denominator
Weighted average common shares outstanding, basic and diluted (shares)	27,301	24,785	21,449
Net (loss) income per share, basic and diluted, continuing operations (in usd per share)	$ (4.62)	$ (2.77)	$ (1.94)