Goodwill and Other Intangibles - Schedule of activity in goodwill (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Aug. 31, 2020	Aug. 31, 2019	May 31, 2020	May 31, 2019
Goodwill [Roll Forward]
Gross goodwill			$ 164.5	$ 164.8
Accumulated impairment			(39.6)	$ (39.6)
Beginning balance	$ 124.9	$ 125.2	125.2
Additions	0.0	0.0	0.0
Foreign currency translation	0.7	(0.2)	(0.3)
Ending balance	$ 125.6	$ 125.0	$ 124.9

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.

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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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.

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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.

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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.

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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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