Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Revenues	$ 85,705	$ 85,573	$ 172,215	$ 168,203
Cost of goods sold	41,132	41,727	83,558	82,048
Gross profit	44,573	43,846	88,657	86,155
Operating expenses
Sales and marketing	10,948	12,130	21,345	22,770
General and administrative	13,293	11,575	25,882	24,118
Research and development	5,795	4,215	10,724	8,204
Total operating expenses	30,036	27,920	57,951	55,092
Operating income	14,537	15,926	30,706	31,063
Interest expense	4,543	4,298	9,135	8,348
Loss on extinguishment of debt	3,196	0	3,196	0
Other income	(1,312)	(336)	(2,499)	(1,256)
Income before income taxes	8,110	11,964	20,874	23,971
Income tax expense	1,698	2,219	4,513	6,015
Net income	$ 6,412	$ 9,745	$ 16,361	$ 17,956
Net income per common share:
Basic (in dollars per share)	$ 0.16	$ 0.25	$ 0.42	$ 0.47
Diluted (in dollars per share)	$ 0.16	$ 0.25	$ 0.41	$ 0.45
Weighted-average common shares outstanding:
Basic (in shares)	38,972	38,233	38,789	38,060
Diluted (in shares)	40,239	39,398	40,064	39,468