Condensed Consolidating Statements Of Cash Flows (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided By Operating Activities	$ 1,291	$ 924
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions of proved and unproved properties	(1,084)	(1,859)
Proceeds from divestitures of proved and unproved properties	49	190
Additions to other property and equipment	(437)	(330)
Other investing activities	473	254
Net Cash Used In Investing Activities	(999)	(1,745)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from credit facilities borrowings	421	3,632
Payments on credit facilities borrowings	(362)	(2,811)
Other financing activities	(184)	(254)
Intercompany advances, net	0	0
Net Cash Provided By (Used In) Financing Activities	(125)	567
Net increase (decrease) in cash and cash equivalents	167	(254)
Cash and cash equivalents, beginning of period	837	287
Cash and cash equivalents, end of period	1,004	33
Parent
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided By Operating Activities	0	0
CASH FLOWS FROM INVESTING ACTIVITIES:
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 credit facilities borrowings	0	0
Payments on credit facilities borrowings	0	0
Other financing activities	(116)	(133)
Intercompany advances, net	291	(95)
Net Cash Provided By (Used In) Financing Activities	175	(228)
Net increase (decrease) in cash and cash equivalents	175	(228)
Cash and cash equivalents, beginning of period	799	228
Cash and cash equivalents, end of period	974	0
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided By Operating Activities	1,027	790
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions of proved and unproved properties	(956)	(1,643)
Proceeds from divestitures of proved and unproved properties	48	138
Additions to other property and equipment	(319)	(186)
Other investing activities	442	135
Net Cash Used In Investing Activities	(785)	(1,556)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from credit facilities borrowings	140	3,395
Payments on credit facilities borrowings	(140)	(2,563)
Other financing activities	47	(94)
Intercompany advances, net	(289)	28
Net Cash Provided By (Used In) Financing Activities	(242)	766
Net increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	0	0
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided By Operating Activities	264	146
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions of proved and unproved properties	(128)	(216)
Proceeds from divestitures of proved and unproved properties	1	52
Additions to other property and equipment	(118)	(144)
Other investing activities	5	74
Net Cash Used In Investing Activities	(240)	(234)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from credit facilities borrowings	281	237
Payments on credit facilities borrowings	(222)	(248)
Other financing activities	(45)	6
Intercompany advances, net	(2)	67
Net Cash Provided By (Used In) Financing Activities	12	62
Net increase (decrease) in cash and cash equivalents	36	(26)
Cash and cash equivalents, beginning of period	39	59
Cash and cash equivalents, end of period	75	33
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided By Operating Activities	0	(12)
CASH FLOWS FROM INVESTING ACTIVITIES:
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	26	45
Net Cash Used In Investing Activities	26	45
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from credit facilities borrowings	0	0
Payments on credit facilities borrowings	0	0
Other financing activities	(70)	(33)
Intercompany advances, net	0	0
Net Cash Provided By (Used In) Financing Activities	(70)	(33)
Net increase (decrease) in cash and cash equivalents	(44)	0
Cash and cash equivalents, beginning of period	(1)	0
Cash and cash equivalents, end of period	$ (45)	$ 0