Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2015
Series C Convertible Preferred Stock [Member]
Issuance of Stock, transaction costs		$ 187
Series D Convertible Preferred Stock [Member]
Issuance of Stock, transaction costs		2,502
Common Stock [Member]
Issuance of Stock, transaction costs	$ 5,738	$ 14,206