Goodwill, Service Contracts and Other Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2016	Nov. 30, 2015	Nov. 30, 2016	Nov. 30, 2015
Goodwill [Line Items]
Amortization expense for continuing operations	$ 3.6	$ 4.2	$ 7.0	$ 7.8
Estimated amortization expense, year one	14.7		14.7
Estimated amortization expense, year two	13.1		13.1
Estimated amortization expense, year three	12.5		12.5
Estimated amortization expense, year four	12.1		12.1
Estimated amortization expense, year five	$ 10.2		$ 10.2