Derivative Instruments and Hedging Activities (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended							12 Months Ended						12 Months Ended				12 Months Ended
	Mar. 30, 2012	Aug. 19, 2010	Oct. 19, 2007	Feb. 16, 2007	Apr. 30, 2012	Apr. 30, 2012 Interest rate swaps [Member]	Apr. 30, 2011 Interest rate swaps [Member]	Apr. 30, 2012 Interest rate swaps [Member] Interest expense [Member]	Apr. 30, 2011 Interest rate swaps [Member] Interest expense [Member]	Apr. 30, 2010 Interest rate swaps [Member] Interest expense [Member]	Apr. 30, 2011 Interest rate swaps [Member] Interest rate swap (term loan) [Member]	Feb. 16, 2007 Interest rate swaps [Member] Interest rate swap (term loan) [Member]	Oct. 19, 2007 Interest rate swaps [Member] Interest rate swap (revolving credit facility) [Member]	Apr. 30, 2011 Interest rate swaps [Member] Interest rate swap (variable rate loans) [Member]	Apr. 30, 2012 Interest rate swaps [Member] Interest rate swap (variable rate loans) [Member]	Mar. 30, 2012 Interest rate swaps [Member] Interest rate swap (variable rate loans) [Member]	Aug. 19, 2010 Interest rate swaps [Member] Interest rate swap (variable rate loans) [Member]	Apr. 30, 2012 Forward exchange contracts [Member] Foreign exchange transaction losses [Member]	Apr. 30, 2011 Forward exchange contracts [Member] Foreign exchange transaction losses [Member]	Apr. 30, 2010 Forward exchange contracts [Member] Foreign exchange transaction losses [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Variable rate loans outstanding					$ 475.0
Derivative [Line Items]
Interest rate swap agreements designated as fully effective cash flow hedges at end of period															2
Interest rate swap agreements designated as fully effective cash flow hedges that expired during the fiscal period											1			1
Fixed interest rate (in hundredths)												5.076%	4.60%			0.645%	0.80%
Fair Value of Interest Rate Swap						1.7	0.5
Basis of variable interest rate, reference rate reset period (in months)												3	3			1	1
Expiration date											Feb. 08, 2011			Aug. 08, 2010
Notional amount of derivative liability																250.0	125.0
Unrecognized loss to be reclassified into net income in the next twelve months						1.4
Debt Instrument, Description of Variable Rate Basis	one month LIBOR	one month LIBOR	three month LIBOR	three month LIBOR
Deferred Loss On Interest Rate Swap recorded as Other Accrued Liabilities						0.5
Deferred Loss On Interest Rate Swap Recorded As Other Long Term Liabilities						1.2
Derivative Instruments, Gain (Loss) [Line Items]
Net losses reclassified from Accumulated Other Comprehensive Loss								0.8	9.1	20.4
(Losses)/gains recognized on derivative instruments																		$ 2.4	$ 0.6	$ (2.0)