Derivative Instruments and Hedging Activities - Schedule of Summary Existing Swap Agreements (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Nov. 30, 2014	May 31, 2014
Outstanding Interest Rate Swap Agreements [Line Items]
Fair Value Asset (Liability)	$ (15.5)	$ (20.2)
September 25, 2014 [Member] | Swap agreements [Member]
Outstanding Interest Rate Swap Agreements [Line Items]
Structure	5 years
Notional Amount	195.0
Effective Date	September 25, 2009
Termination Date	September 25, 2014
Fair Value Asset (Liability)	0	(1.7)
March 25, 2015 [Member] | Swap agreements [Member]
Outstanding Interest Rate Swap Agreements [Line Items]
Structure	2 years
Notional Amount	190.0
Effective Date	March 25, 2013
Termination Date	March 25, 2015
Fair Value Asset (Liability)	(0.4)	(1.0)
September 25, 2016 [Member] | Swap agreements [Member]
Outstanding Interest Rate Swap Agreements [Line Items]
Structure	3 years
Notional Amount	270.0
Effective Date	December 27, 2013
Termination Date	September 25, 2016
Fair Value Asset (Liability)	(4.7)	(5.8)
September 25, 2017 [Member] | Swap agreements [Member]
Outstanding Interest Rate Swap Agreements [Line Items]
Structure	5 years
Notional Amount	350.0
Effective Date	September 25, 2012
Termination Date	September 25, 2017
Fair Value Asset (Liability)	(5.3)	(5.9)
September 25, 2017 [Member] | September 25, 2012 [Member] | Swap agreements [Member]
Outstanding Interest Rate Swap Agreements [Line Items]
Structure	5 years
Notional Amount	350.0
Effective Date	September 25, 2012
Termination Date	September 25, 2017
Fair Value Asset (Liability)	(5.3)	(6.0)
Credit valuation adjustment [Member]
Outstanding Interest Rate Swap Agreements [Line Items]
Fair Value Asset (Liability)	$ 0.2	$ 0.2