Derivative Instruments and Fair Value Measurement (Details) (Fair Value, Inputs, Level 2 [Member], USD $) In Millions	Sep. 30, 2011	Sep. 30, 2010
Assets and liabilities measured at fair value on a recurring basis
Net derivative asset / (liability) designated as hedging instruments	$ 10.2	$ 2.6
Net derivative asset / (liability) not designated as hedging instruments	11.7	5.2
Other current assets [Member]
Assets and liabilities measured at fair value on a recurring basis
Derivatives assets designated as hedging instruments	15.9	9.9
Derivatives assets not designated as hedging instruments	12.1	15.6
Other assets [Member]
Assets and liabilities measured at fair value on a recurring basis
Derivatives assets designated as hedging instruments	1.6	2.7
Other current liabilities [Member]
Assets and liabilities measured at fair value on a recurring basis
Derivatives liabilities designated as hedging instruments	(5.9)	(8.5)
Derivatives liabilities not designated as hedging instruments	(0.4)	(10.4)
Other liabilities [Member]
Assets and liabilities measured at fair value on a recurring basis
Derivatives liabilities designated as hedging instruments	$ (1.4)	$ (1.5)