Revenue - 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]
Allowance for doubtful accounts, balance at beginning of period	$ 19,782	$ 8,171
Bad debt expense	17,336	20,633
Actual write-offs	(11,815)	(9,022)
Allowance for doubtful accounts, balance at end of period	$ 25,303	$ 19,782