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, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator
Net (loss) income from continuing operations	$ (123,716)	$ (126,022)	$ (68,686)
Denominator
Weighted average common shares outstanding, basic and diluted (shares)	37,884	27,301	24,785
Continuing operations (in usd per share)	$ (3.27)	$ (4.62)	$ (2.77)