Business Segment Information (Financial Segment Information By Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Sep. 30, 2023
Segment Reporting Information [Line Items]
Revenue from External Customers	$ 417,442	$ 428,704	$ 1,572,742
Intersegment Revenues	0	0	0
Segment Profit: Net Income (Loss)	(54,158)	92,620	245,134	$ 403,189
Segment Assets:	8,481,037		8,481,037		$ 8,280,260
Total Reportable Segments
Segment Reporting Information [Line Items]
Revenue from External Customers				1,804,824
Corporate and Intersegment Eliminations
Segment Reporting Information [Line Items]
Intersegment Revenues				0
Total Reportable Segments
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)			244,361	401,431
Total Reportable Segments | Total Reportable Segments
Segment Reporting Information [Line Items]
Revenue from External Customers	417,442	428,704	1,572,742	1,804,824
Intersegment Revenues	93,946	83,795		254,151
Segment Profit: Net Income (Loss)	(53,800)	91,314
Segment Assets:	8,630,408		8,630,408		8,402,098
Total Reportable Segments | Corporate and Intersegment Eliminations
Segment Reporting Information [Line Items]
Intersegment Revenues			278,804
Exploration and Production
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)			2,521	195,503
Exploration and Production | Total Reportable Segments
Segment Reporting Information [Line Items]
Revenue from External Customers	220,905	216,581	739,537	738,107
Intersegment Revenues	0	0		0
Segment Profit: Net Income (Loss)	(112,028)	43,329
Segment Assets:	2,815,598		2,815,598		2,814,218
Exploration and Production | Corporate and Intersegment Eliminations
Segment Reporting Information [Line Items]
Intersegment Revenues			0
Pipeline and Storage
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)			85,482	77,147
Pipeline and Storage | Total Reportable Segments
Segment Reporting Information [Line Items]
Revenue from External Customers	68,035	62,956	204,071	194,800
Intersegment Revenues	37,384	29,439		90,354
Segment Profit: Net Income (Loss)	30,690	23,813
Segment Assets:	2,486,740		2,486,740		2,427,214
Pipeline and Storage | Corporate and Intersegment Eliminations
Segment Reporting Information [Line Items]
Intersegment Revenues			103,781
Gathering
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)			82,510	73,207
Gathering | Total Reportable Segments
Segment Reporting Information [Line Items]
Revenue from External Customers	3,644	4,629	12,157	9,003
Intersegment Revenues	56,476	54,277		163,297
Segment Profit: Net Income (Loss)	24,979	24,135
Segment Assets:	998,176		998,176		912,923
Gathering | Corporate and Intersegment Eliminations
Segment Reporting Information [Line Items]
Intersegment Revenues			174,544
Utility
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)			73,848	55,574
Utility | Total Reportable Segments
Segment Reporting Information [Line Items]
Revenue from External Customers	124,858	144,538	616,977	862,914
Intersegment Revenues	86	79		500
Segment Profit: Net Income (Loss)	2,559	37
Segment Assets:	2,329,894		2,329,894		2,247,743
Utility | Corporate and Intersegment Eliminations
Segment Reporting Information [Line Items]
Intersegment Revenues			479
All Other
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)				(430)
All Other | All Other
Segment Reporting Information [Line Items]
Revenue from External Customers	0	0	0	0
Intersegment Revenues	0	0	0	0
Segment Profit: Net Income (Loss)	(124)	(81)	(341)
Segment Assets:	5,067		5,067		4,795
Corporate and Intersegment Eliminations
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)				2,188
Corporate and Intersegment Eliminations | Corporate
Segment Reporting Information [Line Items]
Revenue from External Customers	0	0	0	0
Corporate and Intersegment Eliminations | Corporate and Intersegment Eliminations
Segment Reporting Information [Line Items]
Intersegment Revenues	(93,946)	(83,795)	(278,804)	$ (254,151)
Segment Profit: Net Income (Loss)	(234)	$ 1,387	1,114
Segment Assets:	$ (154,438)		$ (154,438)		$ (126,633)