Income Taxes, Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2023	Mar. 31, 2022
Deferred tax assets [Abstract]
Accounts receivable	$ 0.9	$ 0.8
Inventories	6.0	6.5
Plant and equipment	17.2	19.9
Lease liabilities	15.9	13.5
Pension and employee benefits	24.1	27.5
Net operating and capital losses	55.4	53.9
Credit carryforwards	49.0	48.5
Research and experimental expenditures	8.0	0.0
Other, principally accrued liabilities	13.2	13.5
Total gross deferred tax assets	189.7	184.1
Less: valuation allowances	(61.6)	(112.2)
Net deferred tax assets	128.1	71.9
Deferred tax liabilities [Abstract]
Plant and equipment	7.5	8.6
Lease assets	15.7	13.2
Goodwill	4.8	4.9
Intangible assets	20.1	22.4
Other	1.1	1.5
Total gross deferred tax liabilities	49.2	50.6
Net deferred tax assets	$ 78.9	$ 21.3