Revenue Recognition - Accounts Receivable (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Allowance for Doubtful Accounts
Beginning balance	$ 5,344
Additions charged to costs and expenses	2,431	$ 2,627
Deductions/write-offs	(2,174)
Ending balance	$ 5,601