Accumulated Other Comprehensive Income (Loss) - Reclassification adjustments (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Feb. 28, 2014
Feb. 28, 2013
Feb. 28, 2014
Feb. 28, 2013
Accumulated Other Comprehensive Income Loss [Line Items]        
Reclassification adjustment, interest rate swaps $ (3.7) $ (5.4) $ (25.5) $ (24.4)
Interest Expense [Member]
       
Accumulated Other Comprehensive Income Loss [Line Items]        
Reclassification adjustment, interest rate swaps $ 6.2 $ 9.0 $ 42.3 $ 40.4