Fair Value Measurements (Details) (USD $) In Millions	Jul. 31, 2011
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Commodity derivatives [Member]
Summary of assets and liabilities measured at fair value on a recurring basis
Assets	$ 2.6
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Currency Derivatives [Member]
Summary of assets and liabilities measured at fair value on a recurring basis
Liabilities	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Interest Rate Swap [Member]
Summary of assets and liabilities measured at fair value on a recurring basis
Assets	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Commodity derivatives [Member]
Summary of assets and liabilities measured at fair value on a recurring basis
Assets	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Currency Derivatives [Member]
Summary of assets and liabilities measured at fair value on a recurring basis
Liabilities	18.9
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Interest Rate Swap [Member]
Summary of assets and liabilities measured at fair value on a recurring basis
Assets	4.7
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Commodity derivatives [Member]
Summary of assets and liabilities measured at fair value on a recurring basis
Assets	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Currency Derivatives [Member]
Summary of assets and liabilities measured at fair value on a recurring basis
Liabilities	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Interest Rate Swap [Member]
Summary of assets and liabilities measured at fair value on a recurring basis
Assets	0
Fair Value, Measurements, Recurring [Member] | Commodity derivatives [Member]
Summary of assets and liabilities measured at fair value on a recurring basis
Assets	2.6
Fair Value, Measurements, Recurring [Member] | Currency Derivatives [Member]
Summary of assets and liabilities measured at fair value on a recurring basis
Liabilities	18.9
Fair Value, Measurements, Recurring [Member] | Interest Rate Swap [Member]
Summary of assets and liabilities measured at fair value on a recurring basis
Assets	4.7
Commodity derivatives [Member]
Summary of assets and liabilities measured at fair value on a recurring basis
Assets	2.6
Currency Derivatives [Member]
Summary of assets and liabilities measured at fair value on a recurring basis
Liabilities	18.9
Interest Rate Swap [Member]
Summary of assets and liabilities measured at fair value on a recurring basis
Assets	$ 4.7