Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenues	$ 86,510	$ 82,630
Cost of goods sold	42,426	40,321
Gross profit	44,084	42,309
Operating expenses
Sales and marketing	10,397	10,640
General and administrative	12,589	12,543
Research and development	4,929	3,989
Total operating expenses	27,915	27,172
Operating income	16,169	15,137
Interest expense	4,592	4,050
Other income	(1,187)	(920)
Income before income taxes	12,764	12,007
Income tax expense	2,815	3,796
Net income	$ 9,949	$ 8,211
Net income per common share:
Basic (in dollars per share)	$ 0.26	$ 0.22
Diluted (in dollars per share)	$ 0.25	$ 0.21
Weighted-average common shares outstanding:
Basic (in shares)	38,603	37,886
Diluted (in shares)	39,787	39,493