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Derivative Instruments and Hedging Activities (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Oct. 31, 2018
Oct. 31, 2017
Oct. 31, 2018
Oct. 31, 2017
Apr. 30, 2018
Derivative Instruments and Hedging Activities [Abstract]          
Variable rate loans outstanding $ 537.3   $ 537.3    
Interest Rate Swaps [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Interest Expense [Member]          
Derivative Instruments and Hedging Activities [Abstract]          
Net gain (losses) reclassified from Accumulated Other Comprehensive Loss 1.1 $ 0.3 2.0 $ 0.4  
Interest Rate Swaps [Member] | Recurring [Member] | Level 2 [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]          
Derivative Instruments and Hedging Activities [Abstract]          
Assets fair value of derivative instrument $ 3.3   $ 3.3   $ 5.1
Interest Rate Swaps [Member] | April 2016 Interest Rate Swap (Variable Rate Loans) [Member] | LIBOR [Member]          
Derivative Instruments and Hedging Activities [Abstract]          
Inception date     Apr. 04, 2016    
Fixed interest rate to be paid 0.92%   0.92%    
Term of variable rate     1 month    
Term of derivative instrument     3 years    
Expiration date     May 15, 2019    
Notional amount of derivative liability $ 350.0   $ 350.0   $ 350.0