Derivative Instruments and Fair Value Measurement (Details 1) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Sep. 30, 2014
Fair Value, Inputs, Level 2 [Member]
Assets and liabilities measured at fair value on a recurring basis
Net derivative asset / (liability) designated as hedging instruments	$ 41.6	$ 13.7
Net derivative asset / (liability) not designated as hedging instruments	18.8	1.7
Fair Value, Inputs, Level 2 [Member] \| Other current assets [Member]
Assets and liabilities measured at fair value on a recurring basis
Foreign exchange contracts designated as hedging instruments	49.2	13.1
Foreign exchange contracts not designated as hedging instruments	21.4	3.5
Fair Value, Inputs, Level 2 [Member] \| Other assets [Member]
Assets and liabilities measured at fair value on a recurring basis
Foreign exchange contracts designated as hedging instruments	11.6	5.0
Interest rate swap contracts designated as hedging instruments	1.1	0
Fair Value, Inputs, Level 2 [Member] \| Other current liabilities [Member]
Assets and liabilities measured at fair value on a recurring basis
Foreign exchange contracts designated as hedging instruments	(18.8)	(4.1)
Foreign exchange contracts not designated as hedging instruments	(2.6)	(1.8)
Fair Value, Inputs, Level 2 [Member] \| Other liabilities [Member]
Assets and liabilities measured at fair value on a recurring basis
Foreign exchange contracts designated as hedging instruments	(0.8)	(0.3)
Interest rate swap contracts designated as hedging instruments	(0.7)	0
Foreign Exchange Forward [Member]
Derivatives, Fair Value [Line Items]
Notional amount	1,412.0
Foreign Exchange Forward [Member] \| Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount	223.6
Foreign Exchange Forward [Member] \| Cash Flow Hedging [Member]
Derivatives, Fair Value [Line Items]
Notional amount	736.3
Foreign Exchange Forward [Member] \| Net Investment Hedging [Member]
Derivatives, Fair Value [Line Items]
Notional amount	452.1
Interest Rate Swap [Member] \| Fair Value Hedging [Member]
Derivatives, Fair Value [Line Items]
Notional amount	600.0
Foreign Currency Denominated Debt [Member] \| Net Investment Hedging [Member]
Derivatives, Fair Value [Line Items]
Long-term debt	13.4
Aggregate principal amount of notes issued
Derivatives, Fair Value [Line Items]
Long-term debt	$ 600.0

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

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- Definition

Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

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- Definition

Fair value as of the balance sheet date of all foreign currency derivative assets designated as cash flow hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624163-113959

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Fair value as of the balance sheet date of all foreign currency derivative liabilities designated as cash flow hedging instruments.

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Fair value as of the balance sheet date of all foreign currency derivative assets not designated as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624163-113959

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Fair value as of the balance sheet date of all foreign currency derivatives not designated as hedging instruments.

+ References

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- Definition

Fair value as of the balance sheet date of all foreign currency derivative liabilities not designated as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624163-113959

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- Definition

Fair value as of the balance sheet date of all derivative assets designated as interest rate fair value hedging instruments.

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Fair value as of the balance sheet date of all derivative liabilities designated as interest rate fair value hedging instruments.

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