CONDENSED CONSOLIDATED BALANCE SHEETS(Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Property and equipment, accumulated depreciation	$ 820	$ 758
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	5,000,000.0	5,000,000.0
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000.0	200,000,000
Common stock, shares issued (in shares)	116,627,653	106,801,409
Common stock, shares outstanding (in shares)	116,627,653	106,801,409