Derivative Instruments and Fair Value Measurement (Details) (Fair Value, Inputs, Level 2 [Member], USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Sep. 30, 2011
Assets and liabilities measured at fair value on a recurring basis
Net derivative asset / (liability) designated as hedging instruments	$ 0.1	$ 10.2
Net derivative asset / (liability) not designated as hedging instruments	(10.7)	11.7
Other current assets [Member]
Assets and liabilities measured at fair value on a recurring basis
Derivatives assets designated as hedging instruments	8.7	15.9
Derivatives assets not designated as hedging instruments	2.3	12.1
Other assets [Member]
Assets and liabilities measured at fair value on a recurring basis
Derivatives assets designated as hedging instruments	1.3	1.6
Derivatives assets not designated as hedging instruments	0.1	0
Other current liabilities [Member]
Assets and liabilities measured at fair value on a recurring basis
Derivatives liabilities designated as hedging instruments	(8.4)	(5.9)
Derivatives liabilities not designated as hedging instruments	(13.1)	(0.4)
Other liabilities [Member]
Assets and liabilities measured at fair value on a recurring basis
Derivatives liabilities designated as hedging instruments	$ (1.5)	$ (1.4)