Accounting Policies - Allowance for Doubtful Accounts Rollforward (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Allowance for Doubtful Accounts Rollforward [Line Items]
Additions: charges to costs and expenses	$ 5,672	$ 2,010
Allowance for doubtful accounts rollforward
Allowance for Doubtful Accounts Rollforward [Line Items]
Beginning balance - January 1	8,700
Additions: charges to costs and expenses	5,672
Deductions: returns and write-offs	(972)
Ending balance - June 30	$ 13,400