Note 5 - Property, Plant and Equipment - Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Sep. 28, 2024	Mar. 31, 2024	Sep. 30, 2023
Property, Plant and Equipment, Gross	$ 812,599	$ 772,622	$ 757,051
Less: accumulated depreciation	(486,739)	(467,606)	(451,195)
Property, plant and equipment, net	325,860	305,016	305,856
Land and Land Improvements [Member]
Property, Plant and Equipment, Gross	50,679	49,627	48,385
Building and Building Improvements [Member]
Property, Plant and Equipment, Gross	238,376	236,141	231,736
Machinery and Equipment [Member]
Property, Plant and Equipment, Gross	498,540	457,433	440,206
Office Furniture, Vehicles and Computer Software [Member]
Property, Plant and Equipment, Gross	15,505	14,971	13,149
Construction in Progress [Member]
Property, Plant and Equipment, Gross	$ 9,499	$ 14,450	$ 23,575