Income Taxes - Effective Income Tax Rate Reconciliation (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Taxes
Provision for income taxes	$ 0	$ 0	$ 2,000	$ 3,000
Effective tax rate			0.02%	0.03%