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]
Net sales	$ 138,684	$ 127,073	$ 254,471	$ 221,486
Cost of sales	113,070	109,006	211,153	193,546
Gross profit	25,614	18,067	43,318	27,940
Operating expenses:
Research, development and engineering expenses	6,030	6,962	12,329	12,983
Selling, general and administrative expenses	13,955	13,276	30,015	26,530
Amortization of intangible assets	909	1,321	1,819	2,366
Total operating expenses	20,894	21,559	44,163	41,879
Operating income (loss)	4,720	(3,492)	(845)	(13,939)
Other expense:
Interest expense	2,122	1,828	4,235	3,451
Loss from change in value and exercise of warrants	5,752	6,500	1,352	9,000
Other income, net	(395)	(95)	(501)	(189)
Total other expense	7,479	8,233	5,086	12,262
Loss before income taxes	(2,759)	(11,725)	(5,931)	(26,201)
Income tax expense (benefit)	239	80	(347)	(192)
Net loss	$ (2,998)	$ (11,805)	$ (5,584)	$ (26,009)
Weighted-average common shares outstanding:
Basic (in shares)	21,702	18,594	20,171	18,538
Diluted (in shares)	21,702	18,594	20,171	18,538
Loss per common share:
Basic (in dollars per share)	$ (0.14)	$ (0.63)	$ (0.28)	$ (1.40)
Diluted (in dollars per share)	$ (0.14)	$ (0.63)	$ (0.28)	$ (1.40)