Goodwill, Service Contracts and Other Assets - Narrative (Details) $ in Millions	12 Months Ended
	May. 31, 2015 USD ($) transaction	May. 31, 2014 USD ($)	May. 31, 2013 USD ($)
Goodwill, Service Contracts and Other Assets [Abstract]
Number of transactions involved in sale of business | transaction	3
Continuing Operations
Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 13.7	$ 19.8	$ 20.4
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Estimated amortization expense, year one	11.0
Estimated amortization expense, year two	6.9
Estimated amortization expense, year three	5.9
Estimated amortization expense, year four	5.6
Estimated amortization expense, year five	$ 5.2