Condensed Consolidating Financial Information Statements of Cash Flows Tables (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Cash Provided By Operating Activities	$ 1,595	$ 273
CASH FLOWS FROM INVESTING ACTIVITIES:
Drilling and completion costs	(1,481)	(1,597)
Acquisitions of proved and unproved properties	(244)	(226)
Proceeds from divestitures of proved and unproved properties	395	1,193
Additions to other property and equipment	(11)	(12)
Other investing activities	149	40
Net Cash Used In Investing Activities	(1,192)	(602)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving credit facility borrowings	9,095	4,775
Payments on revolving credit facility borrowings	(9,231)	(4,130)
Proceeds from issuance of senior notes, net	1,237	742
Cash paid to purchase debt	(1,285)	(1,751)
Cash paid for preferred stock dividends	(69)	(160)
Other financing activities	(151)	(24)
Intercompany advances, net	0	0
Net Cash Used In Financing Activities	(404)	(548)
Net decrease in cash and cash equivalents	(1)	(877)
Cash and cash equivalents, beginning of period	5	882
Cash and cash equivalents, end of period	4	5
Eliminations [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Cash Provided By Operating Activities	(10)	(8)
CASH FLOWS FROM INVESTING ACTIVITIES:
Drilling and completion costs	0	0
Acquisitions of proved and unproved properties	0	0
Proceeds from divestitures of proved and unproved properties	0	0
Additions to other property and equipment	0	0
Other investing activities	0	0
Net Cash Used In Investing Activities	0	0
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving credit facility borrowings	0	0
Payments on revolving credit facility borrowings	0	0
Proceeds from issuance of senior notes, net	0	0
Cash paid to purchase debt	0	0
Cash paid for preferred stock dividends	0	0
Other financing activities	(13)	27
Intercompany advances, net	22	0
Net Cash Used In Financing Activities	9	27
Net decrease in cash and cash equivalents	(1)	19
Cash and cash equivalents, beginning of period	(3)	(25)
Cash and cash equivalents, end of period	(4)	(6)
Parent Company [Member] | Reportable legal entities [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Cash Provided By Operating Activities	86	4
CASH FLOWS FROM INVESTING ACTIVITIES:
Drilling and completion costs	0	0
Acquisitions of proved and unproved properties	0	0
Proceeds from divestitures of proved and unproved properties	0	0
Additions to other property and equipment	0	0
Other investing activities	0	0
Net Cash Used In Investing Activities	0	0
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving credit facility borrowings	9,095	4,775
Payments on revolving credit facility borrowings	(9,231)	(4,130)
Proceeds from issuance of senior notes, net	1,237	742
Cash paid to purchase debt	(1,285)	(1,751)
Cash paid for preferred stock dividends	(69)	(160)
Other financing activities	(2)	(36)
Intercompany advances, net	170	(339)
Net Cash Used In Financing Activities	(85)	(899)
Net decrease in cash and cash equivalents	1	(895)
Cash and cash equivalents, beginning of period	5	904
Cash and cash equivalents, end of period	6	9
Guarantor Subsidiaries [Member] | Reportable legal entities [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Cash Provided By Operating Activities	1,512	266
CASH FLOWS FROM INVESTING ACTIVITIES:
Drilling and completion costs	(1,481)	(1,597)
Acquisitions of proved and unproved properties	(244)	(226)
Proceeds from divestitures of proved and unproved properties	395	1,193
Additions to other property and equipment	(11)	(12)
Other investing activities	149	40
Net Cash Used In Investing Activities	(1,192)	(602)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving credit facility borrowings	0	0
Payments on revolving credit facility borrowings	0	0
Proceeds from issuance of senior notes, net	0	0
Cash paid to purchase debt	0	0
Cash paid for preferred stock dividends	0	0
Other financing activities	(127)	(4)
Intercompany advances, net	(193)	339
Net Cash Used In Financing Activities	(320)	335
Net decrease in cash and cash equivalents	0	(1)
Cash and cash equivalents, beginning of period	1	2
Cash and cash equivalents, end of period	1	1
Non-Guarantor Subsidiaries [Member] | Reportable legal entities [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Cash Provided By Operating Activities	7	11
CASH FLOWS FROM INVESTING ACTIVITIES:
Drilling and completion costs	0	0
Acquisitions of proved and unproved properties	0	0
Proceeds from divestitures of proved and unproved properties	0	0
Additions to other property and equipment	0	0
Other investing activities	0	0
Net Cash Used In Investing Activities	0	0
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving credit facility borrowings	0	0
Payments on revolving credit facility borrowings	0	0
Proceeds from issuance of senior notes, net	0	0
Cash paid to purchase debt	0	0
Cash paid for preferred stock dividends	0	0
Other financing activities	(9)	(11)
Intercompany advances, net	1	0
Net Cash Used In Financing Activities	(8)	(11)
Net decrease in cash and cash equivalents	(1)	0
Cash and cash equivalents, beginning of period	2	1
Cash and cash equivalents, end of period	$ 1	$ 1