Condensed Consolidated Statements of Operations and Retained Earnings - USD ($)	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues [Abstract]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 217,142,000	$ 212,828,000	$ 442,134,000	$ 416,554,000
Cost of Goods and Services Sold	141,242,000	141,491,000	286,587,000	276,228,000
Gross Profit	75,900,000	71,337,000	155,547,000	140,326,000
Operating Expenses [Abstract]
Selling expenses	24,515,000	25,042,000	50,082,000	48,842,000
General and administrative expenses	19,688,000	19,433,000	41,514,000	38,386,000
Research and Development Expense	3,118,000	3,723,000	6,866,000	6,645,000
Increase (Decrease) in Assets Held-for-sale	0	0	11,100,000	0
Amortization of intangibles	3,754,000	3,920,000	7,657,000	7,639,000
Operating Expenses	51,075,000	52,118,000	117,219,000	101,512,000
Income from operations	24,825,000	19,219,000	38,328,000	38,814,000
Other Income & Expenses [Abstract]
Interest and debt expense	4,248,000	5,067,000	8,855,000	10,208,000
Investment (income) loss	(111,000)	(46,000)	(379,000)	(108,000)
Foreign currency exchange (gain) loss	507,000	69,000	231,000	393,000
Other (income) expense, net	(307,000)	(429,000)	(347,000)	(988,000)
Income Tax Expense Benefit [Abstract]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	20,488,000	14,558,000	29,968,000	29,309,000
Income tax expense	4,576,000	2,050,000	6,350,000	5,145,000
Net income	15,912,000	12,508,000	23,618,000	24,164,000
Dividends	(1,164,000)	(910,000)	(1,164,000)	(910,000)
Retained Earnings Accumulated Deficit [Abstract]
Retained earnings - beginning of period	206,491,000	191,391,000	197,897,000	179,735,000
Retained earnings - end of period	$ 221,239,000	$ 202,989,000	$ 221,239,000	$ 202,989,000
Weighted Average Number Of Shares Outstanding Basic [Abstract]
Average basic shares outstanding	23,272,000	22,746,000	23,194,000	22,663,000
Weighted Average Number Of Shares Outstanding [Abstract]
Average diluted shares outstanding	23,721,000	23,142,000	23,621,000	23,013,000
Earnings Per Share Basic [Abstract]
Basic income per share:	$ 0.68	$ 0.55	$ 1.02	$ 1.07
Earnings Per Share Diluted [Abstract]
Diluted income per share:	0.67	0.54	1.00	1.05
Common Stock, Dividends, Per Share, Declared	$ 0.05	$ 0.04	$ 0.05	$ 0.04
Accounting Standards Update 2016-01 [Member]
Retained Earnings Accumulated Deficit [Abstract]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 0	$ 0	$ 0	$ 0