Business Segment Information (Financial Segment Information By Segment) (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2022
Segment Reporting Information [Line Items]
Revenue	$ 658,859	$ 546,557
Segment Profit: Net Income (Loss)	169,689	132,392
Segment Assets	8,134,914		$ 7,896,262
Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	658,859	546,557
Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	0	0
Exploration And Production [Member]
Segment Reporting Information [Line Items]
Revenue	276,973	244,198
Segment Profit: Net Income (Loss)	91,192	62,369
Segment Assets	2,531,218		2,507,541
Exploration And Production [Member] | Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	276,973	244,198
Exploration And Production [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	0	0
Pipeline And Storage [Member]
Segment Reporting Information [Line Items]
Revenue	97,655	88,350
Segment Profit: Net Income (Loss)	29,476	25,168
Segment Assets	2,355,063		2,394,697
Pipeline And Storage [Member] | Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	67,621	61,547
Pipeline And Storage [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	30,034	26,803
Gathering [Member]
Segment Reporting Information [Line Items]
Revenue	56,413	52,225
Segment Profit: Net Income (Loss)	24,738	23,137
Segment Assets	894,564		878,796
Gathering [Member] | Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	2,646	4,045
Gathering [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	53,767	48,180
Utility [Member]
Segment Reporting Information [Line Items]
Revenue	311,681	236,759
Segment Profit: Net Income (Loss)	23,817	22,130
Segment Assets	2,392,682		2,299,473
Utility [Member] | Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	311,619	236,684
Utility [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	62	75
Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)	169,223	132,804
Segment Assets	8,173,527		8,080,507
Total Reportable Segments [Member] | Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	658,859	546,474
Total Reportable Segments [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	83,863	75,058
All Other [Member]
Segment Reporting Information [Line Items]
Revenue	0	6
Segment Profit: Net Income (Loss)	(280)	(7)
Segment Assets	1,681		2,036
All Other [Member] | Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	0	0
All Other [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	0	6
Corporate And Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue	(83,863)	(74,981)
Segment Profit: Net Income (Loss)	746	(405)
Segment Assets	(40,294)		$ (186,281)
Corporate And Intersegment Eliminations [Member] | Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	0	83
Corporate And Intersegment Eliminations [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	$ (83,863)	$ (75,064)