For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Long-lived assets other than financial instruments, long-term customer relationships of a financial institution, mortgage and other servicing rights, deferred policy acquisition costs, and deferred tax assets.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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.

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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.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Business Segment Information - Geographic Data (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2017	May 31, 2016	May 31, 2015
Business Segment Information
Long-lived assets	$ 615.6				$ 574.3				$ 615.6	$ 574.3
Sales	492.3	$ 446.7	$ 423.8	$ 404.8	468.6	$ 412.1	$ 431.5	$ 386.7	1,767.6	1,698.9	$ 1,621.4
Aviation Services
Business Segment Information
Sales									1,485.4	1,425.0	1,316.1
Expeditionary Services
Business Segment Information
Sales									282.2	273.9	305.3
United States
Business Segment Information
Long-lived assets	452.8				489.9				452.8	489.9
Europe
Business Segment Information
Long-lived assets	122.5				73.1				122.5	73.1
Other
Business Segment Information
Long-lived assets	$ 40.3				$ 11.3				40.3	11.3
Foreign countries
Business Segment Information
Sales									$ 618.8	$ 494.6	$ 538.9
Foreign countries \| Total sales \| Geographic concentration
Business Segment Information
Percentage of total sales									35.00%	29.10%	33.20%
U.S. Department of Defense, other U.S. government agencies and their contractors
Business Segment Information
Sales									$ 454.8	$ 523.6	$ 495.6
Percentage of total sales									25.70%	30.80%	30.60%
U.S. Department of Defense, other U.S. government agencies and their contractors \| Aviation Services
Business Segment Information
Sales									$ 260.2	$ 301.1	$ 237.3
U.S. Department of Defense, other U.S. government agencies and their contractors \| Expeditionary Services
Business Segment Information
Sales									$ 194.6	$ 222.5	$ 258.3