Financial Instruments and Fair Value Measurements - Recurring Fair Value Measurements (Detail) (Fair Value, Measurements, Recurring [Member], USD $) In Millions, unless otherwise specified	Apr. 30, 2013
Fair Value Assets Measured On Recurring Basis [Line Items]
Total Fair Value	$ (1.5)
Other long-term liabilities [Member] | Interest rate derivatives [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Total Fair Value	(1.3)
Other current assets [Member] | Foreign exchange hedges [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Foreign exchange hedges included in other current assets	0.3
Other current liabilities [Member] | Foreign exchange hedges [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Total Fair Value	(0.5)
Level 2 [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Total Fair Value	(1.5)
Level 2 [Member] | Other long-term liabilities [Member] | Interest rate derivatives [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Total Fair Value	(1.3)
Level 2 [Member] | Other current assets [Member] | Foreign exchange hedges [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Foreign exchange hedges included in other current assets	0.3
Level 2 [Member] | Other current liabilities [Member] | Foreign exchange hedges [Member]
Fair Value Assets Measured On Recurring Basis [Line Items]
Total Fair Value	$ (0.5)