Consolidated Condensed Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net sales	$ 232,677	$ 214,010
Cost of sales	104,228	94,851
Gross profit	128,449	119,159
Selling and administrative expense	98,340	95,867
Research and development expense	10,027	10,120
Operating expenses	108,367	105,987
Income from operations	20,082	13,172
Interest expense	10,351	9,592
Other expense	0	89
Income before income taxes	9,731	3,491
Benefit from income taxes	(129)	(2,436)
Net income	9,860	5,927
Comprehensive income (loss)	$ 10,743	$ (1,121)
Per share data:
Basic (in dollars per share)	$ 0.34	$ 0.21
Diluted (in dollars per share)	$ 0.31	$ 0.20
Weighted average common shares:
Basic (shares)	28,972	28,478
Diluted (shares)	31,378	29,707