Income Taxes, Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2022	Mar. 31, 2021
Deferred tax assets [Abstract]
Accounts receivable	$ 0.8	$ 0.3
Inventories	6.5	4.5
Plant and equipment	19.9	7.5
Lease liabilities	13.5	14.0
Pension and employee benefits	27.5	24.0
Net operating and capital losses	53.9	52.7
Credit carryforwards	48.5	51.8
Other, principally accrued liabilities	13.5	8.9
Total gross deferred tax assets	184.1	163.7
Less: valuation allowances	(112.2)	(90.7)
Net deferred tax assets	71.9	73.0
Deferred tax liabilities [Abstract]
Plant and equipment	8.6	9.8
Lease assets	13.2	13.8
Goodwill	4.9	5.1
Intangible assets	22.4	25.1
Other	1.5	0.6
Total gross deferred tax liabilities	50.6	54.4
Net deferred tax asset	$ 21.3	$ 18.6