Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Nov. 30, 2014	Jan. 31, 2014
Consolidated Statements of Convertible Preferred Stock and Stockholders’ Equity (Deficit)
Stock issuance cost	$ 143	$ 2,046
Series B convertible preferred stock
Consolidated Statements of Convertible Preferred Stock and Stockholders’ Equity (Deficit)
Share price (in dollars per share)			$ 1.20		$ 1.20
Stock issuance cost			$ 115
Series C convertible preferred stock
Consolidated Statements of Convertible Preferred Stock and Stockholders’ Equity (Deficit)
Share price (in dollars per share)			$ 2.07	$ 2.07
Stock issuance cost			$ 131