Accounting Policies - Allowance for Doubtful Accounts Rollforward (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Allowance for Doubtful Accounts Rollforward [Line Items]
Additions: charges to costs and expenses	$ 5,799	$ 2,559
Allowance for doubtful accounts rollforward
Allowance for Doubtful Accounts Rollforward [Line Items]
Beginning balance - January 1	8,700
Additions: charges to costs and expenses	5,799
Deductions: returns and write-offs	(1,099)
Ending balance - September 30	$ 13,400