Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Revenues	$ 79,941	$ 73,063	$ 250,137	$ 227,503
Cost of goods sold	41,414	39,382	125,901	124,370
Gross profit	38,527	33,681	124,236	103,133
Operating expenses
Sales and marketing	10,075	8,706	31,892	27,856
General and administrative	12,076	10,091	35,549	28,842
Research and development	3,554	2,849	14,149	8,493
Total operating expenses	25,705	21,646	81,590	65,191
Gain on sales of assets	0	(560)	0	(6,505)
Operating income	12,822	12,595	42,646	44,447
Interest expense	4,442	6,792	14,147	20,799
Debt retirement costs	0	1,415	0	1,415
Loss on extinguishment of debt	0	0	2,161	0
Other (income) expense	(908)	148	(2,037)	(317)
Income before income taxes	9,288	4,240	28,375	22,550
Provision for income taxes	762	20	2,116	657
Net income	$ 8,526	$ 4,220	$ 26,259	$ 21,893
Net income per common share outstanding
Basic (in dollars per share)	$ 0.23	$ 0.14	$ 0.71	$ 0.71
Diluted (in dollars per share)	$ 0.22	$ 0.13	$ 0.67	$ 0.71
Weighted-average common shares outstanding
Basic (in shares)	37,393	31,221	37,174	30,658
Diluted (in shares)	39,121	32,402	38,971	31,049