Business Segment Information (Details) $ in Millions	3 Months Ended	6 Months Ended
Nov. 30, 2017 USD ($)	Nov. 30, 2016 USD ($)	Nov. 30, 2017 USD ($) segment	Nov. 30, 2016 USD ($)
Business Segment Information
Number of business segments \| segment			2
Sales	$ 449.7	$ 423.8	$ 888.9	$ 828.6
Gross profit (loss)	20.9	66.2	85.4	127.7
Aviation Services
Business Segment Information
Sales	391.6	346.7	762.9	681.3
Gross profit (loss)	66.0	56.0	123.8	109.4
Expeditionary Services
Business Segment Information
Sales	58.1	77.1	126.0	147.3
Gross profit (loss)	$ (45.1)	$ 10.2	$ (38.4)	$ 18.3

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

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 210.5-03.1,2)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

+ 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 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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