Description of Business and Summary of Significant Accounting Policies - Accounts Receivable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts
Beginning Balance	$ 3,070	$ 2,276	$ 1,318
Additions Charged to Costs and Expenses	3,211	2,159	1,788
Deductions / Write-Offs	(1,666)	(1,365)	(830)
ASU 2016-13 (Topic 326) Adjustment	729
Ending Balance	$ 5,344	$ 3,070	$ 2,276