Financial Instruments (Narrative) (Details)	3 Months Ended		12 Months Ended
	Sep. 30, 2022 USD ($) counterparty MMcf		Sep. 30, 2022 USD ($) counterparty MMcf		Jun. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	[1]	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Foreign Currency Forward Contract Hedge Duration			8 years
Net Hedging Gains (Losses) in Accumulated Other Comprehensive Income (Loss)	$ (784,700,000)		$ (784,700,000)
After tax net hedging gains (losses) in accumulated other comprehensive income (Loss)	(572,200,000)		(572,200,000)
Pre-tax Net hedging gains (losses) reclassified within twelve months			(476,700,000)
After tax Net hedging gains (losses) reclassified within twelve months			(347,600,000)
Fair market value of derivative liability with a credit-risk related contingency	564,300,000		564,300,000
Hedging collateral deposits	$ 91,670,000	[1]	$ 91,670,000	[1]		$ 88,610,000		$ 0	$ 6,832,000
Over the Counter Swaps, No Cost Collars and Foreign Currency Forward Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Number of counterparties in which the company holds over-the-counter swap positions | counterparty	19		19
Number of counterparties in net gain position | counterparty	1		1
Credit risk exposure per counterparty	$ 1,000,000		$ 1,000,000
Collateral Received by Company	0		0
Hedging collateral deposits	91,700,000		91,700,000
California Asset Sale [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Maximum Annual Contingent Payment	10,000,000		10,000,000
Amount of Each Incremental Contingent Payment	1,000,000		1,000,000
Incremental Dollar Per Barrel That ICE Brent Average Exceeds Price	1		1
California Asset Sale [Member] | Minimum [Member]
Derivative Instruments, Gain (Loss) [Line Items]
ICE Brent Average per Barrel	95		95
California Asset Sale [Member] | Maximum [Member]
Derivative Instruments, Gain (Loss) [Line Items]
ICE Brent Average per Barrel	105		105
California Asset Sale [Member] | Present Value of Contingent Consideration [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Value of Contingent Consideration from Asset Sale	8,200,000		$ 8,200,000		$ 12,600,000
California Asset Sale [Member] | Mark to Market of Contingent Consideration [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Mark-to-Market Adjustment for Contingent Consideration	$ 4,400,000
Credit Risk Related Contingency Feature [Member] | Over the Counter Swaps, No Cost Collars and Foreign Currency Forward Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Number of counterparties with a common credit-risk related contingency | counterparty	17		17
Foreign Currency Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Notional Amount	$ 49,400,000		$ 49,400,000
Cash Flow Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Hedge Duration			5 years
Cash Flow Hedges [Member] | Natural Gas MMCf [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Nonmonetary notional amount of price risk cash flow hedge derivatives, natural gas | MMcf	420,800		420,800

[1] Netting Adjustments represent the impact of legally-enforceable master netting arrangements that allow the Company to net gain and loss positions held with the same counterparties. The net asset or net liability for each counterparty is recorded as an asset or liability on the Company’s balance sheet.