Segment Information - Reconciliation of Segment Information, (Loss) Earnings Before Income Tax (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	May 02, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Segment Income Before Income Taxes for Reportable Business Segments		$ 192,862	$ 203,434	$ 350,137	$ 992,965
Other (Expense) Income		(3,439)	(1,105)	(2,757)	4,812
Gain on Certain Asset Sales	$ 286	3,308	134,320	610	148,942
Loss on Debt Extinguishment		0	(15,385)	(7,614)	(54,433)
Impairment of Other Intangible Assets		0	0	0	(18,650)
Earnings Before Income Tax		192,862	203,434	350,137	992,965
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Segment Income Before Income Taxes for Reportable Business Segments		192,971	85,604	351,799	290,868
Earnings Before Income Tax		192,971	85,604	351,799	290,868
Corporate, Non-Segment
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Segment Income Before Income Taxes for Reportable Business Segments		(109)	117,830	(1,662)	702,097
Other (Expense) Income		(3,109)	(1,105)	(1,578)	4,811
Gain on Certain Asset Sales		3,000	134,320	7,530	146,706
Gain on Previously Held Equity Interest		0	0	0	623,663
Loss on Debt Extinguishment		0	(15,385)	(7,614)	(54,433)
Impairment of Other Intangible Assets		0	0	0	(18,650)
Earnings Before Income Tax		(109)	117,830	(1,662)	702,097
Total E&P | Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Segment Income Before Income Taxes for Reportable Business Segments		151,230	54,431	233,060	196,366
Earnings Before Income Tax		151,230	54,431	233,060	196,366
Midstream | Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Segment Income Before Income Taxes for Reportable Business Segments		41,741	31,173	118,739	94,502
Earnings Before Income Tax		41,741	31,173	118,739	94,502
Midstream Acquisition | Midstream | Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total Segment Income Before Income Taxes for Reportable Business Segments		41,741	31,173	118,739	94,502
Earnings Before Income Tax		$ 41,741	$ 31,173	$ 118,739	$ 94,502