Fair Value Measurement - Financial Assets and Liabilities that are Measured at Fair Value on a Recurring Basis (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Sep. 30, 2013	Mar. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	$ 23.0	$ 24.2	$ 19.3
Derivative financial instruments, liabilities	(56.7)	(55.4)	(76.3)
Fair Value, Measurements, Recurring | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	22.9	23.3	13.6
Derivative financial instruments, liabilities	(21.1)	(16.0)	(15.3)
Fair Value, Measurements, Recurring | Foreign currency contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	0.1	0.9	1.5
Derivative financial instruments, liabilities	(5.6)	(7.2)	(0.5)
Fair Value, Measurements, Recurring | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets			4.2
Derivative financial instruments, liabilities	(27.8)	(31.0)	(60.5)
Fair Value, Measurements, Recurring | Cross currency swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, liabilities	(2.2)	(1.2)
Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1) | Fair Value, Measurements, Recurring | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	11.5	2.1	7.9
Derivative financial instruments, liabilities	(4.0)	(9.7)	(2.7)
Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1) | Fair Value, Measurements, Recurring | Foreign currency contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	0	0	0
Derivative financial instruments, liabilities	0	0	0
Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1) | Fair Value, Measurements, Recurring | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets			0
Derivative financial instruments, liabilities	0	0	0
Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1) | Fair Value, Measurements, Recurring | Cross currency swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, liabilities	0	0
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	11.4	21.2	5.7
Derivative financial instruments, liabilities	(17.1)	(6.3)	(12.6)
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Foreign currency contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	0.1	0.9	1.5
Derivative financial instruments, liabilities	(5.6)	(7.2)	(0.5)
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets			4.2
Derivative financial instruments, liabilities	(27.8)	(31.0)	(60.5)
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring | Cross currency swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, liabilities	(2.2)	(1.2)
Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	0	0	0
Derivative financial instruments, liabilities	0	0	0
Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Foreign currency contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets	0	0	0
Derivative financial instruments, liabilities	0	0	0
Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets			0
Derivative financial instruments, liabilities	0	0	0
Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring | Cross currency swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, liabilities	$ 0	$ 0