Summary of Significant Accounting Policies - Intangibles (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2022	May 31, 2021	May 31, 2020
Amortizable intangible assets:
Accumulated Amortization	$ (9.1)	$ (19.7)
Unamortized intangible assets:
Trademarks	1.1	1.2
Intangible Assets, Gross (Excluding Goodwill)	12.4	24.2
Intangible Assets, Net (Excluding Goodwill), Total	3.3	4.5
Impairment charge related to exit of certain product line			$ 5.4
Amortization expense	1.1	1.8	$ 2.3
Estimated aggregate amortization expense for intangible assets in each of the next five fiscal years
2023	0.5
2024	0.3
2025	0.3
2026	0.3
2027	0.3
Customer relationships
Amortizable intangible assets:
Gross carrying amount	11.3	23.0
Accumulated Amortization	(9.1)	(19.7)
Net carrying amount	$ 2.2	$ 3.3
Minimum | Customer relationships
Unamortized intangible assets:
Useful life	5 years
Maximum | Customer relationships
Unamortized intangible assets:
Useful life	20 years