Financial Instruments and Fair Value Measurements (Details) (Recurring basis [Member], USD $) In Millions, unless otherwise specified	Apr. 30, 2012
Recurring fair value measurements
Total Fair Value	$ (1.9)
Level 1 [Member]
Recurring fair value measurements
Total Fair Value
Level 2 [Member]
Recurring fair value measurements
Total Fair Value	(1.9)
Level 3 [Member]
Recurring fair value measurements
Total Fair Value
Interest rate derivatives [Member] | Other Long-Term Liabilities [Member]
Recurring fair value measurements
Total Fair Value	(1.1)
Interest rate derivatives [Member] | Level 1 [Member] | Other Long-Term Liabilities [Member]
Recurring fair value measurements
Total Fair Value
Interest rate derivatives [Member] | Level 2 [Member] | Other Long-Term Liabilities [Member]
Recurring fair value measurements
Total Fair Value	(1.1)
Interest rate derivatives [Member] | Level 3 [Member] | Other Long-Term Liabilities [Member]
Recurring fair value measurements
Total Fair Value
Foreign exchange hedges [Member] | Other current assets [Member]
Recurring fair value measurements
Foreign exchange hedges included in other current assets	0.3
Foreign exchange hedges [Member] | Other Current Liabilities [Member]
Recurring fair value measurements
Total Fair Value	(0.4)
Foreign exchange hedges [Member] | Level 1 [Member] | Other current assets [Member]
Recurring fair value measurements
Foreign exchange hedges included in other current assets
Foreign exchange hedges [Member] | Level 1 [Member] | Other Current Liabilities [Member]
Recurring fair value measurements
Total Fair Value
Foreign exchange hedges [Member] | Level 2 [Member] | Other current assets [Member]
Recurring fair value measurements
Foreign exchange hedges included in other current assets	0.3
Foreign exchange hedges [Member] | Level 2 [Member] | Other Current Liabilities [Member]
Recurring fair value measurements
Total Fair Value	(0.4)
Foreign exchange hedges [Member] | Level 3 [Member] | Other current assets [Member]
Recurring fair value measurements
Foreign exchange hedges included in other current assets
Foreign exchange hedges [Member] | Level 3 [Member] | Other Current Liabilities [Member]
Recurring fair value measurements
Total Fair Value
Energy hedges [Member] | Other Current Liabilities [Member]
Recurring fair value measurements
Total Fair Value	(0.7)
Energy hedges [Member] | Level 1 [Member] | Other Current Liabilities [Member]
Recurring fair value measurements
Total Fair Value
Energy hedges [Member] | Level 2 [Member] | Other Current Liabilities [Member]
Recurring fair value measurements
Total Fair Value	(0.7)
Energy hedges [Member] | Level 3 [Member] | Other Current Liabilities [Member]
Recurring fair value measurements
Total Fair Value