Consolidated 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
Common Stock [Member] | IPO [Member]
Stock issuance cost			$ 2,620
Common Stock [Member] | Secondary Offering [Member]
Stock issuance cost	$ 473	$ 866
Series D-2 Preferred [Member] | Issuance Date of February 2014 [Member]
Stock, issuance price per share			$ 0.76
Stock issuance cost			$ 23
Series E Preferred Stock [Member] | Issuance Date of February 2014 [Member]
Stock, issuance price per share			$ 1.13
Stock issuance cost			$ 184