Business Segment Information (Financial Segment Information By Segment) (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Sep. 30, 2023
Segment Reporting Information [Line Items]
Revenue from External Customers	$ 525,361	$ 658,859
Intersegment Revenues	0	0
Segment Profit: Net Income (Loss)	133,020	169,689
Segment Assets:	8,587,492		$ 8,280,260
Total Reportable Segments | Total Reportable Segments
Segment Reporting Information [Line Items]
Revenue from External Customers	525,361	658,859
Intersegment Revenues	87,666	83,863
Segment Profit: Net Income (Loss)	131,914	169,223
Segment Assets:	8,734,487		8,402,098
Exploration and Production | Total Reportable Segments
Segment Reporting Information [Line Items]
Revenue from External Customers	254,019	276,973
Intersegment Revenues	0	0
Segment Profit: Net Income (Loss)	52,483	91,192
Segment Assets:	3,057,345		2,814,218
Pipeline and Storage | Total Reportable Segments
Segment Reporting Information [Line Items]
Revenue from External Customers	64,826	67,621
Intersegment Revenues	29,587	30,034
Segment Profit: Net Income (Loss)	24,055	29,476
Segment Assets:	2,439,479		2,427,214
Gathering | Total Reportable Segments
Segment Reporting Information [Line Items]
Revenue from External Customers	4,596	2,646
Intersegment Revenues	57,992	53,767
Segment Profit: Net Income (Loss)	28,825	24,738
Segment Assets:	936,547		912,923
Utility | Total Reportable Segments
Segment Reporting Information [Line Items]
Revenue from External Customers	201,920	311,619
Intersegment Revenues	87	62
Segment Profit: Net Income (Loss)	26,551	23,817
Segment Assets:	2,301,116		2,247,743
All Other | All Other
Segment Reporting Information [Line Items]
Revenue from External Customers	0	0
Intersegment Revenues	0	0
Segment Profit: Net Income (Loss)	(121)	(280)
Segment Assets:	4,758		4,795
Corporate and Intersegment Eliminations | Corporate
Segment Reporting Information [Line Items]
Revenue from External Customers	0	0
Corporate and Intersegment Eliminations | Corporate and Intersegment Eliminations
Segment Reporting Information [Line Items]
Intersegment Revenues	(87,666)	(83,863)
Segment Profit: Net Income (Loss)	1,227	$ 746
Segment Assets:	$ (151,753)		$ (126,633)