Summary of Significant Accounting Policies (Details 2) $ in Millions	12 Months Ended
	May. 31, 2015 USD ($) item	May. 31, 2014 USD ($)
Goodwill by reportable segment
Goodwill, Beginning Balance	$ 261.7	$ 255.6
Acquisition		0.3
Foreign currency translation adjustments	(1.9)	5.8
Businesses sold or assets held for sale	(136.3)
Goodwill, Ending Balance	$ 123.5	261.7
Number of Reporting Units | item	5
Discontinued operations
Goodwill by reportable segment
Goodwill, Beginning Balance	$ 141.0	136.9
Acquisition		0.3
Foreign currency translation adjustments		3.8
Reallocation of goodwill	(4.7)
Businesses sold or assets held for sale	(136.3)
Goodwill, Ending Balance		141.0
Aviation Services
Goodwill by reportable segment
Goodwill, Beginning Balance	75.7	73.7
Foreign currency translation adjustments	(1.9)	2.0
Goodwill, Ending Balance	73.8	75.7
Expeditionary Services
Goodwill by reportable segment
Goodwill, Beginning Balance	45.0	45.0
Reallocation of goodwill	4.7
Goodwill, Ending Balance	$ 49.7	$ 45.0