Business Segment Information (Segment Information By Segment) (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Dec. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenue			$ 1,742,659	$ 1,546,291	$ 1,693,332
Interest Income			4,388	5,007	6,065
Interest Expense			146,357	117,077	106,756
Depreciation, Depletion and Amortization			335,303	306,158	275,660
Income Tax Expense (Benefit)			114,682	18,739	85,221
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties		$ 76,200	76,152	449,438	0
Gain on Sale of Timber Properties			51,066	0	0
Segment Profit: Net Income (Loss)			363,647	(123,772)	304,290
Expenditures for Additions to Long-Lived Assets			769,911	1,228,617	781,246
Segment Assets			7,464,825	6,964,935	6,462,157
Exploration And Production [Member]
Segment Reporting Information [Line Items]
Revenue			836,697	607,453
Interest Income			211	698	1,107
Interest Expense			69,662	58,098	54,777
Depreciation, Depletion and Amortization			182,492	172,124	154,784
Income Tax Expense (Benefit)			33,370	(41,472)	32,978
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties			76,152	449,438
Gain on Sale of Timber Properties			0
Segment Profit: Net Income (Loss)			101,916	(326,904)	111,807
Expenditures for Additions to Long-Lived Assets			381,408	670,455	491,889
Segment Assets			2,286,058	1,979,028	1,972,776
Pipeline And Storage [Member]
Segment Reporting Information [Line Items]
Revenue			343,557	309,604
Interest Income			1,085	1,475	2,982
Interest Expense			40,976	32,731	29,142
Depreciation, Depletion and Amortization			62,431	53,951	44,947
Income Tax Expense (Benefit)			28,812	28,613	23,238
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties			0	0
Gain on Sale of Timber Properties			0
Segment Profit: Net Income (Loss)			92,542	78,860	74,011
Expenditures for Additions to Long-Lived Assets			252,316	166,652	143,005
Segment Assets			2,296,030	2,204,971	1,893,514
Gathering [Member]
Segment Reporting Information [Line Items]
Revenue			193,264	142,893
Interest Income			259	545	546
Interest Expense			17,493	10,877	9,406
Depreciation, Depletion and Amortization			32,350	22,440	20,038
Income Tax Expense (Benefit)			28,876	18,191	20,895
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties			0	0
Gain on Sale of Timber Properties			0
Segment Profit: Net Income (Loss)			80,274	68,631	58,413
Expenditures for Additions to Long-Lived Assets			34,669	297,806	49,650
Segment Assets			837,729	945,199	547,995
Utility [Member]
Segment Reporting Information [Line Items]
Revenue			667,251	652,298
Interest Income			2,117	2,262	1,809
Interest Expense			21,795	22,150	23,443
Depreciation, Depletion and Amortization			57,457	55,248	53,832
Income Tax Expense (Benefit)			14,007	13,274	13,967
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties			0	0
Gain on Sale of Timber Properties			0
Segment Profit: Net Income (Loss)			54,335	57,366	60,871
Expenditures for Additions to Long-Lived Assets			100,845	94,273	95,847
Segment Assets			2,148,267	2,067,852	1,991,338
Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Revenue			2,040,769	1,712,248
Interest Income			3,672	4,980	6,444
Interest Expense			149,926	123,856	116,768
Depreciation, Depletion and Amortization			334,730	303,763	273,601
Income Tax Expense (Benefit)			105,065	18,606	91,078
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties			76,152	449,438
Gain on Sale of Timber Properties			0
Segment Profit: Net Income (Loss)			329,067	(122,047)	305,102
Expenditures for Additions to Long-Lived Assets			769,238	1,229,186	780,391
Segment Assets			7,568,084	7,197,050	6,405,623
All Other [Member]
Segment Reporting Information [Line Items]
Revenue			1,222	90,271
Interest Income			230	860	1,291
Interest Expense			0	66	21
Depreciation, Depletion and Amortization			394	1,716	1,291
Income Tax Expense (Benefit)			11,438	210	(955)
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties			0	0
Gain on Sale of Timber Properties			51,066
Segment Profit: Net Income (Loss)			37,645	(269)	(1,811)
Expenditures for Additions to Long-Lived Assets			0	39	128
Segment Assets			4,146	113,571	122,241
Corporate And Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue			(299,332)	(256,228)
Interest Income			486	(833)	(1,670)
Interest Expense			(3,569)	(6,845)	(10,033)
Depreciation, Depletion and Amortization			179	679	768
Income Tax Expense (Benefit)			(1,821)	(77)	(4,902)
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties			0	0
Gain on Sale of Timber Properties			0
Segment Profit: Net Income (Loss)			(3,065)	(1,456)	999
Expenditures for Additions to Long-Lived Assets			673	(608)	727
Segment Assets			(107,405)	(345,686)	(65,707)
Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	[1]		1,742,659	1,546,291	1,693,332
Revenue from External Customers [Member] | Exploration And Production [Member]
Segment Reporting Information [Line Items]
Revenue	[1]		836,697	607,453	632,740
Revenue from External Customers [Member] | Pipeline And Storage [Member]
Segment Reporting Information [Line Items]
Revenue	[1]		234,397	205,998	195,808
Revenue from External Customers [Member] | Gathering [Member]
Segment Reporting Information [Line Items]
Revenue	[1]		3,116	72	11
Revenue from External Customers [Member] | Utility [Member]
Segment Reporting Information [Line Items]
Revenue	[1]		666,920	642,855	715,813
Revenue from External Customers [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Revenue	[1]		1,741,130	1,456,378	1,544,372
Revenue from External Customers [Member] | All Other [Member]
Segment Reporting Information [Line Items]
Revenue	[1]		1,173	89,435	148,582
Revenue from External Customers [Member] | Corporate And Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue	[1]		356	478	378
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			109,160	103,606	92,475
Intersegment Revenues [Member] | Gathering [Member]
Segment Reporting Information [Line Items]
Revenue			190,148	142,821	127,064
Intersegment Revenues [Member] | Utility [Member]
Segment Reporting Information [Line Items]
Revenue			331	9,443	11,629
Intersegment Revenues [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Revenue			299,639	255,870	231,168
Intersegment Revenues [Member] | All Other [Member]
Segment Reporting Information [Line Items]
Revenue			49	836	1,127
Intersegment Revenues [Member] | Corporate And Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue			$ (299,688)	$ (256,706)	$ (232,295)

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