Commitments and Contingencies - Rent Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Other Commitments [Line Items]
Rent expense	$ 251	$ 231	$ 487	$ 443
Research and development
Other Commitments [Line Items]
Rent expense	202	200	400	370
Selling, general, and administrative
Other Commitments [Line Items]
Rent expense	$ 49	$ 31	$ 87	$ 73