Business Segment Information - Recon of Gross Profit to Income (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Nov. 30, 2016	Nov. 30, 2015	Nov. 30, 2016	Nov. 30, 2015
Reconciliation of segment gross profit to consolidated income before provision for income taxes
Segment gross profit	$ 66.2	$ 59.1	$ 127.7	$ 113.0
Selling, general and administrative	(46.3)	(43.1)	(91.1)	(83.1)
Loss from joint ventures		(0.1)		(0.4)
Loss on extinguishment of debt		(0.1)		(0.4)
Interest expense	(1.2)	(1.5)	(2.5)	(3.5)
Interest income	0.1		0.1	0.1
Income from continuing operations before provision for income taxes	$ 18.8	$ 14.3	$ 34.2	$ 25.7

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

No definition available.

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- Definition

This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee excluding the discontinued operations portion of earnings from joint ventures.

+ References

No definition available.

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- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12317-112629

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

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

+ References

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

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

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- References

No definition available.

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- Definition

The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. 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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.4)
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