Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for product returns
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 8,510	$ 7,362	$ 11,283
Additions charged to Expense or Revenue	0	1,148	0
Deductions and write-offs	(4,395)	0	(3,921)
Balance at End of Year	4,115	8,510	7,362
Allowance for obsolescence
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	589	768	829
Additions charged to Expense or Revenue	1,204	511	1,192
Deductions and write-offs	(1,074)	(690)	(1,253)
Balance at End of Year	$ 719	$ 589	$ 768