Consolidated Statements of Operations (Unaudited) - USD ($)	3 Months Ended			6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Consolidated Statements of Operations (Unaudited) [Abstract]
Net sales	$ 127,939,000	$ 110,261,000	$ 94,695,000	$ 219,607,000	$ 204,956,000
Cost of goods sold	102,228,000	84,234,000	68,843,000	177,544,000	153,077,000
Gross profit	25,711,000	26,027,000	25,852,000	42,063,000	51,879,000
Operating expenses:
General and administrative	8,997,000	8,615,000	5,888,000	21,088,000	14,503,000
Sales and marketing	4,537,000	3,457,000	3,394,000	8,929,000	6,851,000
Research and development	1,784,000	1,240,000	1,002,000	3,520,000	2,242,000
Total operating expenses	15,318,000	13,312,000	10,284,000	33,537,000	23,596,000
Operating income	10,393,000	12,715,000	15,568,000	8,526,000	28,283,000
Interest expense, net	5,699,000	3,522,000	3,314,000	10,774,000	6,836,000
Income before income tax expense (benefit)	4,694,000	9,193,000	12,254,000	(2,248,000)	21,447,000
Income tax expense (benefit)	1,181,000	3,598,000	4,434,000	(266,000)	8,032,000
Net income (loss)	$ 3,513,000	$ 5,595,000	$ 7,820,000	$ (1,982,000)	$ 13,415,000
Basic net income (loss) per share (in dollars per share)	$ 0.19	$ 0.30	$ 0.42	$ (0.10)	$ 0.72
Diluted net income (loss) per share (in dollars per share)	$ 0.18	$ 0.29	$ 0.40	$ (0.10)	$ 0.69
Weighted average number of shares outstanding:
Basic (in shares)	18,878,674	18,718,709		18,887,214	18,687,179
Diluted (in shares)	19,319,465	19,356,809		18,887,214	19,371,144