Summary of Significant Accounting Policies - New Accounting Pronouncements (Details) - USD ($) $ in Millions	May 31, 2016	May 31, 2015
New Accounting Pronouncements or Change in Accounting Principle
Other	$ 87.0	$ 82.6
Long-term debt, less current maturities	136.1	82.4
Deferred tax liabilities	$ 34.3	46.3
Accounting Standards Update ("ASU") 2015-03 - Simplifying the Presentation of Debt Issuance Costs | Retrospective adjustment
New Accounting Pronouncements or Change in Accounting Principle
Other		(2.6)
Long-term debt, less current maturities		(2.6)
Accounting Standards Update ("ASU") 2015-17 - Income Taxes: Balance Sheet Classification of Deferred Taxes | Retrospective adjustment
New Accounting Pronouncements or Change in Accounting Principle
Deferred tax assets		(58.3)
Deferred tax liabilities		$ (58.3)