Summary of Significant Accounting Policies - Liquidity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Cash and marketable securities	$ 196,400	$ 93,100
Long-term debt	39,455	39,223
Accumulated deficit	239,277	195,580
Net loss	$ (43,697)	$ (38,403)