Business Segment Information - Reconciliation of Gross Profit to Income (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Nov. 30, 2020	Nov. 30, 2019	Nov. 30, 2020	Nov. 30, 2019
Reconciliation of segment gross profit to income from continuing operations before provision for income taxes
Segment gross profit	$ 69.5	$ 85.9	$ 118.1	$ 167.5
Selling, general and administrative	(43.4)	(57.1)	(88.7)	(115.2)
Loss from joint ventures	(0.1)		(0.2)
Provision for doubtful accounts	(4.4)	(0.7)	(4.4)	(1.4)
Loss on sale of business			(19.5)
Other income (expense), net	(0.7)	(0.2)	(0.5)	(0.4)
Interest expense	(1.3)	(1.9)	(3.0)	(4.1)
Interest income		0.1	0.1	0.2
Income from continuing operations before provision for income taxes	$ 19.6	$ 26.1	$ 1.9	$ 46.6

Sum of operating profit and nonoperating income (expense) before income taxes and noncontrolling interest.

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The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses along with impairments. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc.

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Amount of gain (loss) from sale and disposal of integrated set of activities and assets capable of being conducted and managed for purpose of providing return in form of dividend, lower cost, or other economic benefit to investor, owner, member and participant.

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Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

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Amount of income (loss) for proportionate share of equity method investee's income (loss).

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Amount of the cost of borrowed funds accounted for as interest expense.

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Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

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Amount of income (expense) related to nonoperating activities, classified as other.

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Amount of expense (reversal of expense) for expected credit loss on accounts receivable.

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