Consolidated Statements of Income - USD ($)	3 Months Ended								12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Consolidated Statements of Income [Abstract]
Net sales	$ 114,410,000	$ 112,595,000	$ 108,836,000	$ 85,412,000	$ 97,443,000	$ 94,022,000	$ 91,670,000	$ 85,835,000	$ 421,253,000	$ 368,970,000	$ 301,711,000
Cost of goods sold	82,783,000	80,225,000	78,178,000	65,021,000	73,229,000	65,123,000	69,850,000	59,844,000	306,207,000	268,046,000	220,138,000
Gross profit	31,627,000	32,370,000	30,658,000	20,391,000	24,214,000	28,899,000	21,820,000	25,991,000	115,046,000	100,924,000	81,573,000
Operating expenses:
General and administrative	9,678,000	7,952,000	9,869,000	3,625,000	11,284,000	8,802,000	18,219,000	11,360,000	31,124,000	49,665,000	37,863,000
Sales and marketing	3,551,000	3,234,000	2,707,000	2,634,000	2,382,000	2,671,000	2,632,000	2,280,000	12,126,000	9,965,000	7,851,000
Research and development	1,011,000	1,039,000	905,000	869,000	915,000	711,000	646,000	736,000	3,824,000	3,008,000	2,273,000
Total operating expenses	14,240,000	12,225,000	13,481,000	7,128,000	14,581,000	12,184,000	21,497,000	14,376,000	47,074,000	62,638,000	47,987,000
Operating income	17,387,000	20,145,000	17,177,000	13,263,000	9,633,000	16,715,000	323,000	11,615,000	67,972,000	38,286,000	33,586,000
Interest expense, net	3,729,000	3,357,000	3,189,000	2,819,000	2,678,000	2,516,000	2,613,000	8,437,000	13,094,000	16,244,000	13,065,000
Income before income tax expense	13,658,000	16,788,000	13,988,000	10,444,000	6,955,000	14,199,000	(2,290,000)	3,178,000	54,878,000	22,042,000	20,521,000
Income tax expense	3,846,000	5,678,000	4,845,000	2,936,000	4,658,000	6,451,000	(898,000)	1,268,000	17,305,000	11,479,000	9,068,000
Net income	$ 9,812,000	$ 11,110,000	$ 9,143,000	$ 7,508,000	$ 2,297,000	$ 7,748,000	$ (1,392,000)	$ 1,910,000	$ 37,573,000	$ 10,563,000	$ 11,453,000
Basic net income per share (in dollars per share)	$ 0.53	$ 0.59	$ 0.49	$ 0.40	$ 0.12	$ 0.42	$ (0.08)	$ 0.11	$ 2.02	$ 0.58	$ 0.68
Diluted net income per share (in dollars per share)	$ 0.50	$ 0.57	$ 0.47	$ 0.39	$ 0.12	$ 0.41	$ (0.08)	$ 0.10	$ 1.93	$ 0.55	$ 0.65
Weighted average number of shares outstanding:
Basic (in shares)									18,608,812	18,233,163	16,734,539
Diluted (in shares)									19,418,706	19,066,093	17,605,940