Business Segment Information (Segment Information By Segment) (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2022		Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Revenue		$ 2,186,046		$ 1,742,659	$ 1,546,291
Interest Income		6,111		4,388	5,007
Interest Expense		130,357		146,357	117,077
Depreciation, Depletion and Amortization		369,790		335,303	306,158
Income Tax Expense (Benefit)		116,629		114,682	18,739
Significant Item: Gain on Sale of Assets		12,736		51,066	0
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties		0		76,152	449,438
Segment Profit: Net Income (Loss)		566,021		363,647	(123,772)
Expenditures for Additions to Long-Lived Assets		829,388		769,911	1,228,617
Segment Assets		7,896,262		7,464,825	6,964,935
Exploration And Production [Member]
Segment Reporting Information [Line Items]
Revenue		1,010,464		836,697
Interest Income		1,929		211	698
Interest Expense		53,401		69,662	58,098
Depreciation, Depletion and Amortization		208,148		182,492	172,124
Income Tax Expense (Benefit)		43,898		33,370	(41,472)
Significant Item: Gain on Sale of Assets		12,736		0
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties				76,152	449,438
Segment Profit: Net Income (Loss)		306,064		101,916	(326,904)
Expenditures for Additions to Long-Lived Assets		565,791		381,408	670,455
Segment Assets		2,507,541		2,286,058	1,979,028
Pipeline And Storage [Member]
Segment Reporting Information [Line Items]
Revenue		377,044		343,557
Interest Income		2,275		1,085	1,475
Interest Expense		42,492		40,976	32,731
Depreciation, Depletion and Amortization		67,701		62,431	53,951
Income Tax Expense (Benefit)		35,043		28,812	28,613
Significant Item: Gain on Sale of Assets		0		0
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties				0	0
Segment Profit: Net Income (Loss)		102,557		92,542	78,860
Expenditures for Additions to Long-Lived Assets		95,806		252,316	166,652
Segment Assets		2,394,697		2,296,030	2,204,971
Gathering [Member]
Segment Reporting Information [Line Items]
Revenue		214,843		193,264
Interest Income		198		259	545
Interest Expense		16,488		17,493	10,877
Depreciation, Depletion and Amortization		33,998		32,350	22,440
Income Tax Expense (Benefit)		24,949		28,876	18,191
Significant Item: Gain on Sale of Assets		0		0
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties				0	0
Segment Profit: Net Income (Loss)		101,111		80,274	68,631
Expenditures for Additions to Long-Lived Assets		55,546		34,669	297,806
Segment Assets		878,796		837,729	945,199
Utility [Member]
Segment Reporting Information [Line Items]
Revenue		898,221		667,251
Interest Income		2,730		2,117	2,262
Interest Expense		24,115		21,795	22,150
Depreciation, Depletion and Amortization		59,760		57,457	55,248
Income Tax Expense (Benefit)		17,165		14,007	13,274
Significant Item: Gain on Sale of Assets		0		0
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties				0	0
Segment Profit: Net Income (Loss)		68,948		54,335	57,366
Expenditures for Additions to Long-Lived Assets		111,033		100,845	94,273
Segment Assets		2,299,473		2,148,267	2,067,852
Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Revenue		2,500,572		2,040,769
Interest Income		7,132		3,672	4,980
Interest Expense		136,496		149,926	123,856
Depreciation, Depletion and Amortization		369,607		334,730	303,763
Income Tax Expense (Benefit)		121,055		105,065	18,606
Significant Item: Gain on Sale of Assets		12,736		0
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties				76,152	449,438
Segment Profit: Net Income (Loss)		578,680		329,067	(122,047)
Expenditures for Additions to Long-Lived Assets		828,176		769,238	1,229,186
Segment Assets		8,080,507		7,568,084	7,197,050
All Other [Member]
Segment Reporting Information [Line Items]
Revenue		6		1,222
Interest Income		3		230	860
Interest Expense		4		0	66
Depreciation, Depletion and Amortization		0		394	1,716
Income Tax Expense (Benefit)		3		11,438	210
Significant Item: Gain on Sale of Assets		0		51,066
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties				0	0
Segment Profit: Net Income (Loss)		(9)		37,645	(269)
Expenditures for Additions to Long-Lived Assets		0		0	39
Segment Assets		2,036		4,146	113,571
Corporate And Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue		(314,532)		(299,332)
Interest Income		(1,024)		486	(833)
Interest Expense		(6,143)		(3,569)	(6,845)
Depreciation, Depletion and Amortization		183		179	679
Income Tax Expense (Benefit)		(4,429)		(1,821)	(77)
Significant Item: Gain on Sale of Assets		0		0
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties				0	0
Segment Profit: Net Income (Loss)		(12,650)		(3,065)	(1,456)
Expenditures for Additions to Long-Lived Assets		1,212		673	(608)
Segment Assets		(186,281)		(107,405)	(345,686)
Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	[1]	2,186,046		1,742,659	1,546,291
Revenue from External Customers [Member] | Exploration And Production [Member]
Segment Reporting Information [Line Items]
Revenue	[1]	1,010,464	[2]	836,697	607,453
Revenue from External Customers [Member] | Exploration And Production [Member] | Customer Concentration Risk
Segment Reporting Information [Line Items]
Revenue		850,000
Revenue from External Customers [Member] | Pipeline And Storage [Member]
Segment Reporting Information [Line Items]
Revenue	[1]	265,415	[2]	234,397	205,998
Revenue from External Customers [Member] | Pipeline And Storage [Member] | Customer Concentration Risk
Segment Reporting Information [Line Items]
Revenue		15,000
Revenue from External Customers [Member] | Gathering [Member]
Segment Reporting Information [Line Items]
Revenue	[1]	12,086		3,116	72
Revenue from External Customers [Member] | Utility [Member]
Segment Reporting Information [Line Items]
Revenue	[1]	897,916		666,920	642,855
Revenue from External Customers [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Revenue	[1]	2,185,881		1,741,130	1,456,378
Revenue from External Customers [Member] | All Other [Member]
Segment Reporting Information [Line Items]
Revenue	[1]	0		1,173	89,435
Revenue from External Customers [Member] | Corporate And Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue	[1]	165		356	478
Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue		0		0	0
Intersegment Revenues [Member] | Exploration And Production [Member]
Segment Reporting Information [Line Items]
Revenue		0		0	0
Intersegment Revenues [Member] | Pipeline And Storage [Member]
Segment Reporting Information [Line Items]
Revenue		111,629		109,160	103,606
Intersegment Revenues [Member] | Gathering [Member]
Segment Reporting Information [Line Items]
Revenue		202,757		190,148	142,821
Intersegment Revenues [Member] | Utility [Member]
Segment Reporting Information [Line Items]
Revenue		305		331	9,443
Intersegment Revenues [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Revenue		314,691		299,639	255,870
Intersegment Revenues [Member] | All Other [Member]
Segment Reporting Information [Line Items]
Revenue		6		49	836
Intersegment Revenues [Member] | Corporate And Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue		$ (314,697)		$ (299,688)	$ (256,706)

[1] All Revenue from External Customers originated in the United States.

[2] Revenues from three customers of the Company's Exploration and Production segment, exclusive of hedging losses transacted with separate parties, represented approximately $850 million of the Company's consolidated revenue for the year ended September 30, 2022. These three customers were also customers of the Company's Pipeline and Storage segment, accounting for an additional $15 million of the Company's consolidated revenue for the year ended September 30, 2022.