Business Segment Information (Segment Information By Segment) (Details) - USD ($) $ in Thousands		3 Months Ended													12 Months Ended
		Sep. 30, 2015		Jun. 30, 2015		Mar. 31, 2015		Dec. 31, 2014	Sep. 30, 2014		Jun. 30, 2014	Mar. 31, 2014	[4]	Dec. 31, 2013	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting Information [Line Items]
Interest Income															$ 3,922	$ 4,170	$ 4,335
Interest Expense															99,471	94,277	94,111
Depreciation, Depletion and Amortization															336,158	383,781	326,760
Income Tax Expense (Benefit)															(319,136)	189,614	172,758
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties		$ 417,200		$ 588,700		$ 120,300									1,126,257	0	0
Segment Profit: Net Income (Loss)		(187,703)	[1]	$ (293,134)	[2]	$ 16,669	[3]	$ 84,741	$ 57,431	[2]	$ 64,520	$ 95,210		$ 82,252	(379,427)	299,413	260,001
Expenditures for Additions to Long-Lived Assets															1,000,509	969,907	717,097
Segment Assets		6,702,139							6,728,040						6,702,139	6,728,040	6,204,977
Utility [Member]
Segment Reporting Information [Line Items]
Interest Income															2,220	3,010	3,417
Interest Expense															28,176	27,693	29,076
Depreciation, Depletion and Amortization															45,616	43,594	42,729
Income Tax Expense (Benefit)															33,143	33,918	31,065
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties															0
Segment Profit: Net Income (Loss)															63,271	64,059	65,686
Expenditures for Additions to Long-Lived Assets															94,371	88,810	71,970
Segment Assets		1,960,158							1,862,850						1,960,158	1,862,850	1,870,587
Pipeline And Storage [Member]
Segment Reporting Information [Line Items]
Interest Income															474	284	193
Interest Expense															27,658	26,428	26,248
Depreciation, Depletion and Amortization															38,178	36,642	35,156
Income Tax Expense (Benefit)															48,113	47,100	38,626
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties															0
Segment Profit: Net Income (Loss)															80,354	77,559	63,245
Expenditures for Additions to Long-Lived Assets															230,192	139,821	56,144
Segment Assets		1,597,173							1,367,181						1,597,173	1,367,181	1,246,027
Exploration And Production [Member]
Segment Reporting Information [Line Items]
Interest Income															2,554	1,909	1,501
Interest Expense															46,726	42,232	39,745
Depreciation, Depletion and Amortization															239,818	296,210	243,431
Income Tax Expense (Benefit)															(428,217)	81,370	95,317
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties															1,126,257
Segment Profit: Net Income (Loss)															(556,974)	121,569	115,391
Expenditures for Additions to Long-Lived Assets															557,313	602,705	533,129
Segment Assets		2,549,374							3,100,514						2,549,374	3,100,514	2,746,233
Energy Marketing [Member]
Segment Reporting Information [Line Items]
Interest Income															195	173	169
Interest Expense															27	31	36
Depreciation, Depletion and Amortization															209	197	123
Income Tax Expense (Benefit)															4,547	3,761	2,450
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties															0
Segment Profit: Net Income (Loss)															7,766	6,631	4,589
Expenditures for Additions to Long-Lived Assets															128	264	595
Segment Assets		88,193							76,238						88,193	76,238	67,267
Gathering [Member]
Segment Reporting Information [Line Items]
Interest Income															140	120	55
Interest Expense															1,627	1,726	2,283
Depreciation, Depletion and Amortization															10,829	6,116	3,945
Income Tax Expense (Benefit)															24,721	23,636	10,287
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties															0
Segment Profit: Net Income (Loss)															31,849	32,709	13,321
Expenditures for Additions to Long-Lived Assets															118,166	137,799	54,792
Segment Assets		447,968							326,662						447,968	326,662	203,323
Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Interest Income															5,583	5,496	5,335
Interest Expense															104,214	98,110	97,388
Depreciation, Depletion and Amortization															334,650	382,759	325,384
Income Tax Expense (Benefit)															(317,693)	189,785	177,745
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties															1,126,257
Segment Profit: Net Income (Loss)															(373,734)	302,527	262,232
Expenditures for Additions to Long-Lived Assets															1,000,170	969,399	716,630
Segment Assets		6,642,866							6,733,445						6,642,866	6,733,445	6,133,437
All Other [Member]
Segment Reporting Information [Line Items]
Interest Income															66	106	115
Interest Expense															0	6	2
Depreciation, Depletion and Amortization															832	344	577
Income Tax Expense (Benefit)															13	822	529
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties															0
Segment Profit: Net Income (Loss)															(2)	1,160	894
Expenditures for Additions to Long-Lived Assets															0	274	307
Segment Assets		77,350							86,460						77,350	86,460	95,793
Corporate And Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Interest Income															(1,727)	(1,432)	(1,115)
Interest Expense															(4,743)	(3,839)	(3,279)
Depreciation, Depletion and Amortization															676	678	799
Income Tax Expense (Benefit)															(1,456)	(993)	(5,516)
Significant Non-Cash Item: Impairment of Oil and Gas Producing Properties															0
Segment Profit: Net Income (Loss)															(5,691)	(4,274)	(3,125)
Expenditures for Additions to Long-Lived Assets															339	234	160
Segment Assets		$ (18,077)							$ (91,865)						(18,077)	(91,865)	(24,253)
Revenue From External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	[5]														1,760,913	2,113,081	1,829,551
Revenue From External Customers [Member] | Utility [Member]
Segment Reporting Information [Line Items]
Revenue	[5]														700,761	831,156	730,319
Revenue From External Customers [Member] | Pipeline And Storage [Member]
Segment Reporting Information [Line Items]
Revenue	[5]														203,089	200,664	178,184
Revenue From External Customers [Member] | Exploration And Production [Member]
Segment Reporting Information [Line Items]
Revenue	[5]														693,441	804,096	702,937
Revenue From External Customers [Member] | Energy Marketing [Member]
Segment Reporting Information [Line Items]
Revenue	[5]														159,857	271,993	211,990
Revenue From External Customers [Member] | Gathering [Member]
Segment Reporting Information [Line Items]
Revenue	[5]														497	673	1,324
Revenue From External Customers [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Revenue	[5]														1,757,645	2,108,582	1,824,754
Revenue From External Customers [Member] | All Other [Member]
Segment Reporting Information [Line Items]
Revenue	[5]														2,352	3,532	3,910
Revenue From External Customers [Member] | Corporate And Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue	[5]														916	967	887
Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue															0	0	0
Intersegment Revenues [Member] | Utility [Member]
Segment Reporting Information [Line Items]
Revenue															15,506	18,462	16,020
Intersegment Revenues [Member] | Pipeline And Storage [Member]
Segment Reporting Information [Line Items]
Revenue															88,251	83,744	89,424
Intersegment Revenues [Member] | Exploration And Production [Member]
Segment Reporting Information [Line Items]
Revenue															0	0	0
Intersegment Revenues [Member] | Energy Marketing [Member]
Segment Reporting Information [Line Items]
Revenue															849	1,159	1,384
Intersegment Revenues [Member] | Gathering [Member]
Segment Reporting Information [Line Items]
Revenue															76,709	69,937	33,457
Intersegment Revenues [Member] | Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Revenue															181,315	173,302	140,285
Intersegment Revenues [Member] | All Other [Member]
Segment Reporting Information [Line Items]
Revenue															0	0	0
Intersegment Revenues [Member] | Corporate And Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue															$ (181,315)	$ (173,302)	$ (140,285)

[1] Includes a non-cash $417.2 million impairment charge ($240.9 million after tax) associated with the Exploration and Production segment's oil and gas producing properties and a $8.0 million reversal of stock-based compensation expense ($5.2 million after tax) related to performance based restricted stock units.

[2] Includes a non-cash $588.7 million impairment charge ($339.8 million after tax) associated with the Exploration and Production segment's oil and gas producing properties.

[3] Includes a non-cash $120.3 million impairment charge ($69.5 million after tax) associated with the Exploration and Production segment's oil and gas producing properties.

[4] Includes $3.6 million of income associated with a death benefit gain on life insurance proceeds recorded in the Corporate category.

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