Condensed Consolidated Statements of Operations and Retained Earnings - USD ($)	3 Months Ended		6 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues [Abstract]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 207,609,000	$ 217,142,000	$ 420,321,000	$ 442,134,000
Cost of Goods and Services Sold	134,116,000	141,242,000	271,216,000	286,587,000
Gross Profit	73,493,000	75,900,000	149,105,000	155,547,000
Operating Expenses [Abstract]
Selling expenses	22,877,000	24,515,000	45,632,000	50,082,000
General and administrative expenses	19,153,000	19,688,000	38,753,000	41,514,000
Research and Development Expense	2,999,000	3,118,000	5,791,000	6,866,000
Impairment of Long-Lived Assets to be Disposed of	7,000	0	176,000	11,100,000
Amortization of intangibles	3,226,000	3,754,000	6,479,000	7,657,000
Operating Expenses	48,262,000	51,075,000	96,831,000	117,219,000
Income from operations	25,231,000	24,825,000	52,274,000	38,328,000
Other Income & Expenses [Abstract]
Interest and debt expense	3,759,000	4,248,000	7,611,000	8,855,000
Investment (income) loss	(229,000)	(111,000)	(531,000)	(379,000)
Foreign currency exchange (gain) loss	(296,000)	507,000	(706,000)	231,000
Other (income) expense, net	257,000	(307,000)	419,000	(347,000)
Income Tax Expense Benefit [Abstract]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	21,740,000	20,488,000	45,481,000	29,968,000
Income tax expense	5,141,000	4,576,000	10,303,000	6,350,000
Net income	16,599,000	15,912,000	35,178,000	23,618,000
Retained Earnings Accumulated Deficit [Abstract]
Retained earnings - beginning of period	255,038,000	206,491,000	236,459,000	197,897,000
Retained earnings - end of period	$ 270,218,000	$ 221,239,000	$ 270,218,000	$ 221,239,000
Weighted Average Number Of Shares Outstanding Basic [Abstract]
Average basic shares outstanding	23,631,000	23,272,000	23,532,000	23,194,000
Weighted Average Number Of Shares Outstanding [Abstract]
Average diluted shares outstanding	23,926,000	23,721,000	23,832,000	23,621,000
Earnings Per Share Basic [Abstract]
Basic income per share:	$ 0.70	$ 0.68	$ 1.49	$ 1.02
Earnings Per Share Diluted [Abstract]
Diluted income per share:	0.69	0.67	1.48	1.00
Common Stock, Dividends, Per Share, Declared	$ 0.06	$ 0.05	$ 0.06	$ 0.05