SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts
Movement in Valuation Allowances and Reserves
Balance at Beginning of Period	$ 5,181	$ 4,813	$ 4,471
Charged to Costs and Expenses	342	1,481	588
Net (Deductions) Recoveries	(708)	(1,113)	(246)
Balance at End of Period	4,815	5,181	4,813
Deferred tax asset valuation allowance
Movement in Valuation Allowances and Reserves
Balance at Beginning of Period	471	445	3,994
Net (Deductions) Recoveries	19	26	(3,549)
Balance at End of Period	490	471	445
Reserve for obsolete or slow moving inventory
Movement in Valuation Allowances and Reserves
Balance at Beginning of Period	10,467	10,169	3,875
Charged to Costs and Expenses	5,826	6,467	8,088
Net (Deductions) Recoveries	(2,464)	(6,169)	(1,794)
Balance at End of Period	$ 13,829	$ 10,467	$ 10,169