Goodwill and Other Intangibles - Schedule of activity in goodwill (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Aug. 31, 2021	Aug. 31, 2020	May 31, 2021	May 31, 2020
Goodwill [Roll Forward]
Gross goodwill			$ 165.9	$ 164.5
Accumulated impairment			(39.6)	$ (39.6)
Beginning balance	$ 126.3	$ 124.9	124.9
Foreign currency translation	(0.4)	0.7	1.4
Ending balance	$ 125.9	$ 125.6	$ 126.3

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
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- Definition

Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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Amount before accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
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-Paragraph 1
-Subparagraph (a)
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Amount of accumulated impairment loss for an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
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-URI http://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

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

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