Note 10 - Income Taxes - Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Mar. 31, 2022
Future tax credits	$ 5,007	$ 5,245
Inventory valuation	8,364	3,024
Employee benefits	2,335	2,191
Insurance	471	345
State depreciation basis differences	3,218	0
Operating leases	942	0
Intangibles	1,514	0
Other comprehensive loss	7,117	8,975
Interest	8	3
Prepaid revenue	296	374
Net operating loss and other tax attribute carryovers	1,233	614
Other	327	0
Total assets	30,832	20,771
Property basis and depreciation difference	26,450	21,805
Inventory reserve	2,101	0
Intangibles	0	17
Right-of-use assets	7,045	5,764
Pension	21,528	21,253
Other	182	1,017
Total liabilities	(57,306)	(49,856)
Valuation allowance - noncurrent	(5,007)	(3,931)
Deferred income tax liability, net	$ (31,481)	$ (33,016)