Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for doubtful accounts receivable
Deducted from asset accounts:
Balance at Beginning of Period	$ 616	$ 640	$ 857
Charged to Costs and Expenses	(39)	271	84
Charged to Other Accounts	0	0	0
Deduction	185	295	301
Balance at End of Period	392	616	640
Inventory reserves and obsolescence
Deducted from asset accounts:
Balance at Beginning of Period	12,026	13,176	14,407
Charged to Costs and Expenses	2,238	3,341	3,521
Charged to Other Accounts	0	0	0
Deduction	735	4,491	4,752
Balance at End of Period	$ 13,529	$ 12,026	$ 13,176