Background and Organization - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Background And Organization [Line Items]
Net loss from operations	$ 27,961	$ 13,368
Net cash used from operations	11,964	10,490
Cash and cash equivalents	49,301	$ 5,729	$ 14,198	$ 20,667
2017 Private Placement Common Stock Warrants
Background And Organization [Line Items]
Proceed from private placement and equity issuances, gross	$ 48,000