Reconciliation of Segment Information, Income (Loss) From Continuing Operations Before Income Tax (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Segment Income (Loss) Before Income Taxes for reportable business segments	$ 30,292	$ 179,765	$ 789,532	$ 41,337
Other (Expense) Income	(575)	(5,475)	5,917	(9,550)
Gain on Certain Asset Sales	3,280	134,581	14,622	138,577
(Loss) Gain on Debt Extinguishment	(23,413)	(36)	(39,048)	786
Impairment of Other Intangible Assets	(18,650)	0	(18,650)	0
Income From Continuing Operations Before Income Tax	30,292	179,765	789,532	41,337
Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Segment Income (Loss) Before Income Taxes for reportable business segments	69,920	50,695	205,264	(88,476)
Income From Continuing Operations Before Income Tax	69,920	50,695	205,264	(88,476)
Corporate, Non-Segment [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Segment Income (Loss) Before Income Taxes for reportable business segments	(39,628)	129,070	584,268	129,813
Other (Expense) Income	(575)	(5,475)	5,917	(9,550)
Gain on Certain Asset Sales	3,010	134,581	12,386	138,577
Gain on Previously Held Equity Interest	0	0	623,663	0
(Loss) Gain on Debt Extinguishment	(23,413)	(36)	(39,048)	786
Impairment of Other Intangible Assets	(18,650)	0	(18,650)	0
Income From Continuing Operations Before Income Tax	(39,628)	129,070	584,268	129,813
Total E&P [Member] \| Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Segment Income (Loss) Before Income Taxes for reportable business segments	42,125	50,695	141,935	(88,476)
Income From Continuing Operations Before Income Tax	42,125	50,695	141,935	(88,476)
Midstream [Member] \| Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Segment Income (Loss) Before Income Taxes for reportable business segments	27,795	0	63,329	0
Income From Continuing Operations Before Income Tax	$ 27,795	$ 0	$ 63,329	$ 0

Amount of gain (loss) on sale or disposal of an equity method investment.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(b)(7)(c))
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(b)(9)(a))
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

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