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Derivative Financial Instruments and Fair Value Measurements - Cash Flow Hedges (Details) - Designated as Hedging Instrument - Cash Flow Hedging AUD in Millions, $ in Millions | Dec. 31, 2017 AUD | Dec. 31, 2017 USD ($) | Sep. 30, 2017 AUD | Sep. 30, 2017 USD ($)
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Interest Rate Swap June 2018 |  |  |  |
Derivative financial instruments |  |  |  |
Notional Amount |  | $ 300.0 |  | $ 300.0
Fixed Rate (as a percent) | 1.63% | 1.63% | 1.63% | 1.63%
Interest Rate Swap September 2018 |  |  |  |
Derivative financial instruments |  |  |  |
Notional Amount |  | $ 300.0 |  | $ 300.0
Fixed Rate (as a percent) | 1.54% | 1.54% | 1.54% | 1.54%
Foreign currency contracts |  |  |  |
Derivative financial instruments |  |  |  |
Notional principal of derivative exchange contracts | AUD 13.2 | $ 9.9 | AUD 15.1 | $ 11.3

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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. + References No definition available. + Details
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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 + Details
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- Details
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