Derivative Financial Instruments Outstanding Interest Rate Swap Agreements (Details) AUD in Thousands, $ in Thousands			12 Months Ended
	Sep. 30, 2026 USD ($)	Sep. 30, 2020	Dec. 31, 2017 AUD	Dec. 31, 2017 USD ($)
Interest Rate Swap 3 [Member]
Derivatives [Line Items]
Effective Date			Sep. 30, 2016
Expiration Date			Sep. 30, 2026
Notional Amount | $				$ 100,000
Derivative, Forward Interest Rate			2.76%	2.76%
Interest Rate Swap 4 [Member]
Derivatives [Line Items]
Effective Date			Sep. 30, 2016
Expiration Date			Sep. 30, 2026
Notional Amount | $				$ 100,000
Derivative, Forward Interest Rate			2.74%	2.74%
Interest Rate Swap 5 [Member]
Derivatives [Line Items]
Effective Date			Sep. 30, 2016
Expiration Date			Sep. 30, 2026
Notional Amount | $				$ 100,000
Derivative, Forward Interest Rate			2.73%	2.73%
Interest Rate Swap 6 [Member]
Derivatives [Line Items]
Effective Date			Dec. 01, 2016
Expiration Date			Dec. 01, 2021
Notional Amount			AUD 93,150
Derivative, Forward Interest Rate			2.44%	2.44%
Interest Rate Swap 7 [Member]
Derivatives [Line Items]
Effective Date			Dec. 01, 2016
Expiration Date			Dec. 01, 2021
Notional Amount			AUD 93,150
Derivative, Forward Interest Rate			2.44%	2.44%
Interest Rate Swap 8 [Member]
Derivatives [Line Items]
Effective Date			Dec. 01, 2016
Expiration Date			Dec. 01, 2021
Notional Amount			AUD 93,150
Derivative, Forward Interest Rate			2.44%	2.44%
Interest Rate Swap 9 [Member]
Derivatives [Line Items]
Effective Date			Dec. 01, 2016
Expiration Date			Dec. 01, 2021
Notional Amount			AUD 93,150
Derivative, Forward Interest Rate			2.44%	2.44%
Interest Rate Swap 10 [Member]
Derivatives [Line Items]
Effective Date			Dec. 01, 2016
Expiration Date			Dec. 01, 2021
Notional Amount			AUD 55,373
Derivative, Forward Interest Rate			2.44%	2.44%
Interest Rate Swap 11 [Member]
Derivatives [Line Items]
Effective Date			Dec. 01, 2016
Expiration Date			Dec. 01, 2021
Notional Amount			AUD 55,373
Derivative, Forward Interest Rate			2.44%	2.44%
Interest Rate Swap 12 [Member]
Derivatives [Line Items]
Effective Date			Dec. 01, 2016
Expiration Date			Dec. 01, 2021
Notional Amount			AUD 34,155
Derivative, Forward Interest Rate			2.44%	2.44%
Scenario, Forecast [Member] | Interest Rate Swap [Member]
Derivatives [Line Items]
Expiration Date	Sep. 30, 2026
Derivative, Settlement Date		Sep. 30, 2020
Fixed rate debt [Member] | Scenario, Forecast [Member]
Derivatives [Line Items]
Probable future borrowings | $	$ 300,000
Variable rate debt [Member] | Scenario, Forecast [Member]
Derivatives [Line Items]
Probable future borrowings | $	$ 300,000