Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=51831255

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Business Segment Information (Financial Segment Information By Segment) (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2016
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)	$ 88,908	$ (189,109)
Segment Assets	5,661,717		$ 5,636,387
Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	422,500	375,195
Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	0	0
Exploration And Production [Member]
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)	35,080	(237,086)
Segment Assets	1,267,468		1,323,081
Exploration And Production [Member] \| Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	160,932	151,965
Exploration And Production [Member] \| Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	0	0
Pipeline And Storage [Member]
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)	19,368	21,276
Segment Assets	1,698,279		1,680,734
Pipeline And Storage [Member] \| Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	53,000	53,354
Pipeline And Storage [Member] \| Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	22,155	22,183
Gathering [Member]
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)	10,981	4,921
Segment Assets	552,855		534,259
Gathering [Member] \| Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	26	125
Gathering [Member] \| Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	27,840	18,640
Utility [Member]
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)	21,175	18,606
Segment Assets	2,071,276		2,021,514
Utility [Member] \| Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	170,971	143,848
Utility [Member] \| Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	1,826	3,664
Energy Marketing [Member]
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)	1,782	1,223
Segment Assets	77,454		63,392
Energy Marketing [Member] \| Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	36,809	24,984
Energy Marketing [Member] \| Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	19	311
Total Reportable Segments [Member]
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)	88,386	(191,060)
Segment Assets	5,667,332		5,622,980
Total Reportable Segments [Member] \| Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	421,738	374,276
Total Reportable Segments [Member] \| Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	51,840	44,798
All Other [Member]
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)	(179)	189
Segment Assets	76,857		77,138
All Other [Member] \| Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	554	706
All Other [Member] \| Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	0	0
Corporate And Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Segment Profit: Net Income (Loss)	701	1,762
Segment Assets	(82,472)		$ (63,731)
Corporate And Intersegment Eliminations [Member] \| Revenue from External Customers [Member]
Segment Reporting Information [Line Items]
Revenue	208	213
Corporate And Intersegment Eliminations [Member] \| Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	$ (51,840)	$ (44,798)