Fair Value Measurement (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Sep. 30, 2011	Mar. 31, 2011
Fair Value, Measurements, Recurring [Member] | Commodity contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	$ 11.0	$ 6.8	$ 14.7
Derivative financial instruments, liabilities	(83.3)	(44.2)	(20.4)
Fair Value, Measurements, Recurring [Member] | Foreign currency contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	3.1	5.3	0.3
Derivative financial instruments, liabilities		(3.3)	(4.0)
Fair Value, Measurements, Recurring [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets			13.0
Derivative financial instruments, liabilities	(53.2)	(44.4)	(0.2)
Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1) [Member] | Foreign currency contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets
Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1) [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, liabilities
Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | Commodity contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	9.8	3.5	2.6
Derivative financial instruments, liabilities	(41.1)	(28.1)	(10.6)
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Commodity contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	1.2	3.3	12.1
Derivative financial instruments, liabilities	(42.2)	(16.1)	(9.8)
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Foreign currency contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	3.1	5.3	0.3
Derivative financial instruments, liabilities		(3.3)	(4.0)
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets			13.0
Derivative financial instruments, liabilities	(53.2)	(44.4)	(0.2)
Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Commodity contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets
Derivative financial instruments, liabilities
Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Foreign currency contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets
Derivative financial instruments, liabilities
Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets
Derivative financial instruments, liabilities