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Derivative Financial Instruments and Fair Value Measurements (Details) AUD in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2016 USD ($)	Sep. 30, 2015 item	Dec. 31, 2016 AUD	Dec. 31, 2016 USD ($)	Sep. 30, 2016 AUD	Sep. 30, 2016 USD ($)
Derivative financial instruments
Number of contingent consideration arrangements | item		1
Material subsequent changes in fair value	$ 0
Level 3
Derivative financial instruments
Fair value of contingent consideration liability				$ 22,000,000		$ 39,000,000
Designated as Hedging Instrument | Cash Flow Hedging | Interest rate swap agreements
Derivative financial instruments
Losses Recognized in Income on Derivatives (Amount Excluded from Effectiveness Testing and Ineffective Portion)	$ 0
Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap June 2018
Derivative financial instruments
Notional Amount				$ 300,000,000		$ 300,000,000
Fixed Rate (as a percent)			1.63%	1.63%	1.63%	1.63%
Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap September 2018
Derivative financial instruments
Notional Amount				$ 300,000,000		$ 300,000,000
Fixed Rate (as a percent)			1.54%	1.54%	1.54%	1.54%
Designated as Hedging Instrument | Cash Flow Hedging | Foreign currency forward contracts
Derivative financial instruments
Notional principal of derivative exchange contracts			AUD 44.1	$ 32,900,000	AUD 58.6	$ 43,400,000

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- Definition

Fair value, as of the acquisition date, of potential payments under the contingent consideration arrangement including cash and shares.

+ References

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The number of contingent consideration arrangements entered by the entity in relation to payment of consideration for acquisition in connection with certain financial performance.

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- Definition

Aggregate notional amount of foreign currency derivatives to exchange foreign currencies. Notional amount refers to the number of currency units specified in the foreign currency derivative contract.

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- Definition

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

+ References

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

The net increase or decrease in fair value as a result of changes in the assumptions or model used to calculate the fair value of servicing assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(4)(i)
-URI http://asc.fasb.org/extlink&oid=56950315&loc=d3e122625-111746

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Fixed interest rate related to the interest rate derivative.

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- Definition

The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
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-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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