Taxes - Schedule of unrecognized tax benefits (Details) - USD ($) $ in Millions	12 Months Ended
May 31, 2025	May 31, 2024	May 31, 2023
Unrecognized Tax Benefits [Roll Forward]
Gross unrecognized benefits, Beginning of period	$ 1.8	$ 2.0	$ 3.1
Decreases related to prior year tax positions	0.0	(0.8)	(1.7)
Increase related to prior year tax positions	0.1	0.7	0.1
Increases related to current year tax positions	0.1	0.1	0.5
Settlements during the period	0.0	(0.2)	0.0
Lapse of statute of limitation	(0.8)	0.0	0.0
Gross unrecognized benefits, End of period	$ 1.2	$ 1.8	$ 2.0

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 217
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- Definition

Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

+ References

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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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- Definition

Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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- Definition

Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

+ References

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