Financial Instruments Balance Sheet Location (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
ASSETS
Net Financial Instruments	$ 80,678	$ 1,811
Liabilities
Net Financial Instruments	(2,015)	(5,801)
Designated as Hedging Instrument
ASSETS
Gross / Net Financial Instruments	73,055
Liabilities
Gross / Net Financial Instruments	0
Designated as Hedging Instrument | Deferred Charges And Other Assets | Interest rate agreements
ASSETS
Gross / Net Financial Instruments	73,055
Designated as Hedging Instrument | Deferred Credits And Other Liabilities | Interest rate agreements
Liabilities
Gross / Net Financial Instruments	0
Not Designated as Hedging Instrument
ASSETS
Gross / Net Financial Instruments	7,623	1,811
Liabilities
Gross / Net Financial Instruments	(2,015)	(5,801)
Not Designated as Hedging Instrument | Other Current Assets | Commodity contracts
ASSETS
Gross / Net Financial Instruments	5,687	1,586
Not Designated as Hedging Instrument | Deferred Charges And Other Assets | Commodity contracts
ASSETS
Gross / Net Financial Instruments	1,936	225
Not Designated as Hedging Instrument | Other Current Liabilities | Commodity contracts
Liabilities
Gross / Net Financial Instruments	(2,015)	(4,552)
Not Designated as Hedging Instrument | Deferred Credits And Other Liabilities | Commodity contracts
Liabilities
Gross / Net Financial Instruments	$ 0	$ (1,249)