Schedule II - Valuation and Qualifying Accounts and Reserves (Details) - Accounts Receivable - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Movement in Valuation Allowances and Reserves
Balance at beginning of year	$ 3,350	$ 2,038	$ 3,782
Additions Charged Against Revenue	5,895	3,039	8,886
Additions Charged to Cost and Expense	1,855	3,520	0
Deductions	(7,749)	(5,247)	(10,630)
Balance at end of year	$ 3,351	$ 3,350	$ 2,038