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Derivatives and Fair Value Measurements Texuals (Details) AUD in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2018 $ / AUD	Dec. 31, 2017 AUD
Predecessor
Derivatives, Fair Value [Line Items]
Currency Options | $	$ 257.3
Foreign Exchange Contract [Member] | Successor
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount | AUD				AUD 1,125.0
Minimum | Foreign Exchange Contract [Member] | Scenario, Forecast
Derivatives, Fair Value [Line Items]
Derivative, Exchange Rate Cap | $ / AUD			0.79
Maximum | Foreign Exchange Contract [Member] | Scenario, Forecast
Derivatives, Fair Value [Line Items]
Derivative, Exchange Rate Cap | $ / AUD			0.83
Gains realized on previously monetized foreign currency cash flow hedges [Member] | Predecessor
Derivatives, Fair Value [Line Items]
Foreign Currency Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net | $		$ 14.9

X

- 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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X

- Definition

Cap rate on a foreign currency derivative for example, but not limited to, a cap or a collar.

+ References

No definition available.

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+ References

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- Definition

Amount of settlements of financial instrument classified as a derivative asset (liability) after deduction of derivative liability, measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19279-110258

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- Definition

The amount of net gains or losses on foreign currency cash flow hedges reclassified during the period to earnings from accumulated other comprehensive income upon the hedged transaction affecting earnings.

+ 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 (c)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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