Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Feb. 28, 2018	Feb. 28, 2017	Feb. 28, 2018	Feb. 28, 2017	May 31, 2017
Revenue Recognition
Recognized net favorable cumulative catch-up adjustments	$ 1.8	$ 3.2	$ 2.2	$ 7.8
Sales from support services	181.2	164.5	510.0	461.2
Gross profit on support services	77.6	66.5	209.9	185.5
KC10 logistics support services
Revenue Recognition
Sales from support services	3.6	24.3	24.6	92.3
Gross profit on support services	0.2	$ 1.6	2.4	$ 6.1
KC10 Supply Program
Revenue Recognition
Unbilled accounts receivable related to KC10 program	$ 5.4		$ 5.4		$ 14.5

Amount of recognized favorable cumulative catch-up adjustments under revenue recognition.

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- Definition

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

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

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Aggregate revenue during the period from services rendered in the normal course of business, after deducting allowances and 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(d))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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- Definition

Unbilled amounts due for services rendered or to be rendered, actions taken or to be taken, or a promise to refrain from taking certain actions in accordance with the terms of a legally binding agreement between the entity and, at a minimum, one other party. An example would be amounts associated with contracts or programs where the recognized revenue for performance thereunder exceeds the amounts billed under the terms thereof as of the date of the balance sheet.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3(c)(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 912
-SubTopic 310
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=68054760&loc=d3e55302-109406

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