Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 942	$ 1,119	$ 977
Charged to Income	313	146	321
Deductions from Reserves	(160)	(323)	(179)
Other Adjustments	(7)	0	0
Balance at End of Year	1,088	942	1,119
Rebates and allowances
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	6,985	4,654	2,860
Charged to Income	19,675	16,729	13,202
Deductions from Reserves	(16,706)	(14,237)	(11,047)
Other Adjustments	(604)	(161)	(361)
Balance at End of Year	$ 9,350	$ 6,985	$ 4,654