Supplementary Information For Oil And Gas Producing Activities (Results Of Operations For Producing Activities) (Details) - USD ($)		12 Months Ended
		Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Reserve Quantities [Line Items]
Revenues from sales to affiliates		$ 0	$ 0	$ 0
Operating Revenues	[1]	1,881,680,000	915,668,000	510,291,000
Production/Lifting Costs		283,914,000	267,316,000	203,670,000
Franchise/Ad Valorem Taxes		25,112,000	22,128,000	15,582,000
Purchased Emission Allowance Expense		1,305,000	2,940,000	2,930,000
Accretion Expense		7,530,000	7,743,000	5,237,000
Depreciation, Depletion and Amortization ($0.57, $0.54 and $0.69 per Mcfe of production)		202,418,000	177,055,000	166,759,000
Impairment of Oil and Gas Producing Properties		0	76,152,000	449,438,000
Income Tax Expense		368,925,000	98,593,000	(92,820,000)
Results of Operations for Producing Activities (excluding corporate overheads and interest charges)		992,476,000	263,741,000	(240,505,000)
Depreciation, Depletion and Amortization, per Mcfe of Production		0.57	0.54	0.69
Transfers to Entity's Other Operations		5,696,000	3,061,000	1,921,000
Natural Gas [Member]
Reserve Quantities [Line Items]
Gas (includes transfers to operations of $5,696, $3,061 and $1,921, respectively)	[2]	1,730,723,000	780,477,000	402,447,000
Oil, Condensate And Other Liquids [Member]
Reserve Quantities [Line Items]
Operating Revenues		$ 150,957,000	$ 135,191,000	$ 107,844,000

[1] Exclusive of hedging gains and losses. See further discussion in Note J — Financial Instruments.

[2] There were no revenues from sales to affiliates for all years presented.