| Goodwill and Intangible Assets, Net of Accumulated Amortization (Narrative) (Details) - USD ($) $ in Millions | 3 Months Ended | ||
|---|---|---|---|
| Aug. 31, 2017 | Aug. 31, 2016 | May 31, 2017 | |
| Goodwill and Intangible Assets, Net of Accumulated Amortization [Abstract] | |||
| Goodwill | $ 698.0 | $ 657.1 | |
| Increased in goodwill result of HROI acquisition | 40.9 | ||
| Amortization expense | $ 3.9 | $ 4.4 | |
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- Definition The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- References No definition available. 
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