Fair Value of Financial Instruments - Fair Value Derivative Liability (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2021	Sep. 30, 2020
Derivative Liability, Fair Value, Gross Liability [Roll Forward]
Balance at beginning of period	$ 1,930	$ 2,500	$ 2,420	$ 2,420
Change in fair value of derivative liability, recorded as other expense (income)	0	(570)	80	(490)	$ 340
Balance at end of period	$ 1,930	$ 1,930	$ 2,500	$ 1,930