CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Net sales	$ 115,787	$ 94,413
Cost of sales	98,083	84,540
Gross profit	17,704	9,873
Operating expenses:
Research, development and engineering expenses	6,299	6,021
Selling, general and administrative expenses	16,060	13,254
Amortization of intangible assets	910	1,045
Total operating expenses	23,269	20,320
Operating loss	(5,565)	(10,447)
Other (income) expense:
Interest expense	2,113	1,623
(Gain) loss from change in value of warrants	(4,400)	2,500
Other income, net	(106)	(94)
Total other (income) expense	(2,393)	4,029
Loss before income taxes	(3,172)	(14,476)
Income tax benefit	(586)	(272)
Net loss	$ (2,586)	$ (14,204)
Weighted-average common shares outstanding:
Basic (in shares)	18,639	18,483
Diluted (in shares)	22,635	18,483
Loss per common share:
Basic (in dollars per share)	$ (0.14)	$ (0.77)
Diluted (in dollars per share)	$ (0.31)	$ (0.77)