Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Private Placement
Offering cost	$ 0	$ 111	$ 529
Direct Registered Offering
Offering cost	177	81	0
Public Offering
Offering cost	10,631	0	0
At The Market Offering Program
Offering cost	$ 6	$ 1,147	$ 0