Supplementary Information For Oil And Gas Producing Activities (Proved Developed And Undeveloped Oil And Gas Reserve Quantities) (Details) ft³ in Billions		12 Months Ended
		Sep. 30, 2022 MMcf MBbls ft³	Sep. 30, 2021 MMcf MBbls ft³	Sep. 30, 2020 MMcf MBbls ft³	Sep. 30, 2019 MMcf MBbls
Reserve Quantities [Line Items]
Proved Undeveloped Reserve (Volume) | ft³		858	636	551
Natural Gas (Mmcf) [Member]
Reserve Quantities [Line Items]
Proved Developed and Undeveloped Reserves		3,723,433	3,325,085	2,949,519
Extensions and Discoveries		837,510	689,395	7,246
Revisions of Previous Estimates		2,953	22,973	(88,419)
Production Volume		(342,911)	(314,020)	(227,402)
Purchases of Minerals in Place				684,141
Sales of Minerals in Place		(50,323)
Proved Developed and Undeveloped Reserves		4,170,662	3,723,433	3,325,085
Proved Developed Reserves (Volume)		3,312,568	3,091,463	2,773,823	1,934,795
Proved Undeveloped Reserve (Volume)		858,094	631,970	551,262	1,014,724
Oil Mbbl [Member]
Reserve Quantities [Line Items]
Proved Developed and Undeveloped Reserves | MBbls		21,537	22,100	24,873
Extensions and Discoveries | MBbls		296	1,041	288
Revisions of Previous Estimates | MBbls		787	631	(713)
Production Volume		(1,604)	(2,235)	(2,348)
Sales of Minerals in Place | MBbls		(20,766)
Proved Developed and Undeveloped Reserves | MBbls		250	21,537	22,100
Proved Developed Reserves (Volume) | MBbls		250	20,941	22,100	24,259
Proved Undeveloped Reserve (Volume) | MBbls		0	596	0	614
West Coast Region [Member]
Reserve Quantities [Line Items]
Proved Undeveloped Reserve (Volume) | ft³		0	5
West Coast Region [Member] | Natural Gas (Mmcf) [Member]
Reserve Quantities [Line Items]
Proved Developed and Undeveloped Reserves		30,285	28,972	33,633
Extensions and Discoveries		0	0	0
Revisions of Previous Estimates		71	3,033	(2,772)
Production Volume		(1,211)	(1,720)	(1,889)
Purchases of Minerals in Place				0
Sales of Minerals in Place		(29,145)
Proved Developed and Undeveloped Reserves		0	30,285	28,972
Proved Developed Reserves (Volume)		0	30,285	28,972	33,633
Proved Undeveloped Reserve (Volume)		0	0	0	0
West Coast Region [Member] | Oil Mbbl [Member]
Reserve Quantities [Line Items]
Proved Developed and Undeveloped Reserves | MBbls		21,526	22,088	24,860
Extensions and Discoveries | MBbls		296	1,041	288
Revisions of Previous Estimates | MBbls		532	630	(715)
Production Volume		(1,588)	(2,233)	(2,345)
Sales of Minerals in Place | MBbls		(20,766)
Proved Developed and Undeveloped Reserves | MBbls		0	21,526	22,088
Proved Developed Reserves (Volume) | MBbls		0	20,930	22,088	24,246
Proved Undeveloped Reserve (Volume) | MBbls		0	596	0	614
Appalachian Region [Member] | Natural Gas (Mmcf) [Member]
Reserve Quantities [Line Items]
Proved Developed and Undeveloped Reserves		3,693,148	3,296,113	2,915,886
Extensions and Discoveries	[1]	837,510	689,395	7,246
Revisions of Previous Estimates		2,882	19,940	(85,647)
Production Volume	[2]	(341,700)	(312,300)	(225,513)
Purchases of Minerals in Place				684,141
Sales of Minerals in Place		(21,178)
Proved Developed and Undeveloped Reserves		4,170,662	3,693,148	3,296,113
Proved Developed Reserves (Volume)		3,312,568	3,061,178	2,744,851	1,901,162
Proved Undeveloped Reserve (Volume)		858,094	631,970	551,262	1,014,724
Appalachian Region [Member] | Oil Mbbl [Member]
Reserve Quantities [Line Items]
Proved Developed and Undeveloped Reserves | MBbls		11	12	13
Extensions and Discoveries | MBbls		0	0	0
Revisions of Previous Estimates | MBbls		255	1	2
Production Volume		(16)	(2)	(3)
Sales of Minerals in Place | MBbls		0
Proved Developed and Undeveloped Reserves | MBbls		250	11	12
Proved Developed Reserves (Volume) | MBbls		250	11	12	13
Proved Undeveloped Reserve (Volume) | MBbls		0	0	0	0
Marcellus Shale Fields [Member]
Reserve Quantities [Line Items]
Proved Undeveloped Reserve (Volume) | ft³		355	220	287
Marcellus Shale Fields [Member] | Natural Gas (Mmcf) [Member]
Reserve Quantities [Line Items]
Extensions and Discoveries		301,000	180,000	7,000
Production Volume		(209,463)	(218,016)	(169,453)
Percentage exceeding total reserve of production in proved developed and undeveloped reserves		15.00%
Utica Shale [Member]
Reserve Quantities [Line Items]
Proved Undeveloped Reserve (Volume) | ft³		503	411	265
Utica Shale [Member] | Natural Gas (Mmcf) [Member]
Reserve Quantities [Line Items]
Extensions and Discoveries		537,000	497,000	0
Production Volume		(130,240)	(93,253)	(55,392)
Percentage exceeding total reserve of production in proved developed and undeveloped reserves		15.00%

[1] Extensions and discoveries include 7 Bcf (during 2020), 180 Bcf (during 2021) and 301 Bcf (during 2022), of Marcellus Shale gas (which exceed 15% of total reserves) in the Appalachian region. Extensions and discoveries include 0 Bcf (during 2020), 497 Bcf (during 2021) and 537 Bcf (during 2022), of Utica Shale gas (which exceed 15% of total reserves) in the Appalachian region.

[2] Production includes 169,453 MMcf (during 2020), 218,016 MMcf (during 2021) and 209,463 MMcf (during 2022), from Marcellus Shale fields. Production includes 55,392 MMcf (during 2020), 93,253 MMcf (during 2021) and 130,240 MMcf (during 2022), from Utica Shale fields.