Condensed Consolidating Statements Of Cash Flows (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Condensed Financial Statements, Captions [Line Items]
Cash provided by operating activities	$ 2,205	$ 1,029
CASH FLOWS FROM INVESTING ACTIVITIES:
Additions to proved and unproved properties	(3,695)	(6,915)
Proceeds from divestitures of proved and unproved properties	1,895	1,555
Additions to other property and equipment	(506)	(1,311)
Other investing activities	731	1,750
Cash used in investing activities	(1,575)	(4,921)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from credit facilities borrowings	6,559	10,104
Payments on credit facilities borrowings	(6,578)	(11,592)
Proceeds from issuance of senior notes, net of discount and offering costs	2,274	1,263
Cash paid to purchase debt	(1,874)	0
Proceeds from issuance of term loans, net of discount and offering costs	0	3,789
Proceeds from sales of noncontrolling interests	5	1,039
Other financing activities	(626)	(31)
Intercompany advances, net	0	0
Cash provided by financing activities	(240)	4,572
Change in cash and cash equivalents classified as current assets held for sale	0	(7)
Net increase (decrease) in cash and cash equivalents	390	673
Cash and cash equivalents, beginning of period	287	351
Cash and cash equivalents, end of period	677	1,024
Parent
Condensed Financial Statements, Captions [Line Items]
Cash provided by operating activities	0	0
CASH FLOWS FROM INVESTING ACTIVITIES:
Additions to 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
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
Proceeds from issuance of senior notes, net of discount and offering costs	2,274	1,263
Cash paid to purchase debt	(1,874)
Proceeds from issuance of term loans, net of discount and offering costs		3,789
Proceeds from sales of noncontrolling interests	0	0
Other financing activities	(245)	(235)
Intercompany advances, net	(155)	(4,817)
Cash provided by financing activities	0	0
Change in cash and cash equivalents classified as current assets held for sale		0
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
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash provided by operating activities	1,933	1,846
CASH FLOWS FROM INVESTING ACTIVITIES:
Additions to proved and unproved properties	(3,238)	(6,693)
Proceeds from divestitures of proved and unproved properties	1,834	1,555
Additions to other property and equipment	(316)	(429)
Other investing activities	161	3,426
Cash used in investing activities	(1,559)	(2,141)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from credit facilities borrowings	6,013	7,990
Payments on credit facilities borrowings	(6,013)	(9,709)
Proceeds from issuance of senior notes, net of discount and offering costs	0	0
Cash paid to purchase debt	0
Proceeds from issuance of term loans, net of discount and offering costs		0
Proceeds from sales of noncontrolling interests	5	0
Other financing activities	(292)	117
Intercompany advances, net	340	2,807
Cash provided by financing activities	53	1,205
Change in cash and cash equivalents classified as current assets held for sale		0
Net increase (decrease) in cash and cash equivalents	427	910
Cash and cash equivalents, beginning of period	228	1
Cash and cash equivalents, end of period	655	911
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash provided by operating activities	297	128
CASH FLOWS FROM INVESTING ACTIVITIES:
Additions to proved and unproved properties	(457)	(222)
Proceeds from divestitures of proved and unproved properties	61	0
Additions to other property and equipment	(190)	(882)
Other investing activities	440	(171)
Cash used in investing activities	(146)	(1,275)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from credit facilities borrowings	546	2,114
Payments on credit facilities borrowings	(565)	(1,883)
Proceeds from issuance of senior notes, net of discount and offering costs	0	0
Cash paid to purchase debt	0
Proceeds from issuance of term loans, net of discount and offering costs		0
Proceeds from sales of noncontrolling interests	0	1,039
Other financing activities	16	(2,363)
Intercompany advances, net	(185)	2,010
Cash provided by financing activities	(188)	917
Change in cash and cash equivalents classified as current assets held for sale		(7)
Net increase (decrease) in cash and cash equivalents	(37)	(237)
Cash and cash equivalents, beginning of period	59	350
Cash and cash equivalents, end of period	22	113
Eliminations
Condensed Financial Statements, Captions [Line Items]
Cash provided by operating activities	(25)	(945)
CASH FLOWS FROM INVESTING ACTIVITIES:
Additions to 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	130	(1,505)
Cash used in investing activities	130	(1,505)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from credit facilities borrowings	0	0
Payments on credit facilities borrowings	0	0
Proceeds from issuance of senior notes, net of discount and offering costs	0	0
Cash paid to purchase debt	0
Proceeds from issuance of term loans, net of discount and offering costs		0
Proceeds from sales of noncontrolling interests	0	0
Other financing activities	(105)	2,450
Intercompany advances, net	0	0
Cash provided by financing activities	(105)	2,450
Change in cash and cash equivalents classified as current assets held for sale		0
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