Summary of Significant Accounting Policies - Concentration (Details)	9 Months Ended		12 Months Ended
	Sep. 30, 2021 customer USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2020 customer
Sales | Customer
Risk and Uncertainties
Number of customers exceeding 10% of benchmark | $	0	0
Accounts receivable | Credit
Risk and Uncertainties
Number of customers exceeding 10% of benchmark | customer	0		0