Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements (Financial Liabilities Measured at Fair Value on Non-Recurring Basis) (Details)

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Fair Value Measurements (Financial Liabilities Measured at Fair Value on Non-Recurring Basis) (Details) - USD ($)
$ in Millions
Nov. 30, 2019
May 31, 2019
Debt Instrument [Line Items]    
Total long-term borrowings, Amortized cost $ 800.0 $ 800.0
Less: Debt issuance costs, net of accumulated amortization, Amortized cost (3.4) (3.6)
Long-term borrowings, net of debt issuance costs, Amortized cost 796.6 796.4
Senior Notes [Member]    
Debt Instrument [Line Items]    
Total long-term borrowings, Amortized cost 800.0 800.0
Senior Notes, Series A [Member] | Senior Notes [Member]    
Debt Instrument [Line Items]    
Total long-term borrowings, Amortized cost 400.0 400.0
Senior Notes, Series B [Member] | Senior Notes [Member]    
Debt Instrument [Line Items]    
Total long-term borrowings, Amortized cost 400.0 400.0
Non-Recurring Basis [Member]    
Debt Instrument [Line Items]    
Total long-term borrowings, Fair value 864.2 838.5
Less: Debt issuance costs, net of accumulated amortization, Fair value (3.4) (3.6)
Long-term borrowings, net of debt issuance costs, Fair value 860.8 834.9
Non-Recurring Basis [Member] | Senior Notes, Series A [Member] | Senior Notes [Member]    
Debt Instrument [Line Items]    
Total long-term borrowings, Fair value 430.0 418.4
Non-Recurring Basis [Member] | Senior Notes, Series B [Member] | Senior Notes [Member]    
Debt Instrument [Line Items]    
Total long-term borrowings, Fair value $ 434.2 $ 420.1