Employee Benefit Plans - Schedule of recognized in accumulated other comprehensive loss (Details) - USD ($) $ in Millions	May 31, 2022	May 31, 2021
Pension and postretirement adjustments:
Actuarial gain (loss)	$ (7.0)	$ (11.8)
Prior service credit (cost)	8.4	9.2
Amount recognized in Accumulated comprehensive income (loss) net of tax	(0.8)	(4.6)
U.K. \| Pension Plans
Pension and postretirement adjustments:
Actuarial gain (loss)	(7.4)	(10.4)
Prior service credit (cost)	0.0	(0.0)
Amount recognized in Accumulated comprehensive income (loss) net of tax	(7.4)	(10.4)
U.S. \| Other Postretirement Benefits
Pension and postretirement adjustments:
Actuarial gain (loss)	0.4	(1.4)
Prior service credit (cost)	8.4	9.2
Amount recognized in Accumulated comprehensive income (loss) net of tax	$ 6.6	$ 5.8

Amount, after tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
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-URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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-Publisher FASB
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- Definition

Amount, before tax, of accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (j)
-URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669686-108580

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Amount, before tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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