Accounts Receivable - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at the beginning of the year	$ (1,219)	$ 0
Increase in the allowance for doubtful accounts	(340)	(1,219)
Balance at the end of the year	$ (1,559)	$ (1,219)