Net Loss Per Share - Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Reconciliation of net loss attributable to common stockholders for basic and diluted net loss per share
Net loss attributable to common stockholders basic		$ (17,124)
Interest expense on 2026 Convertible Note		356
Change in fair value of derivative liability		(3,223)
Net loss attributable to common stockholders, diluted		$ (19,991)
Weighted average common shares outstanding, basic	51,900,882	42,251,292
Shares issuable upon conversion of 2026 Convertible Note, as if converted		1,923,077
Weighted average common shares outstanding, diluted	51,900,882	44,174,369
Net loss per share attributable to common stockholders, diluted	$ (0.41)	$ (0.45)