Change in Accounting Principle - Statement of Consolidated Cash Flow (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015		Sep. 30, 2016		Sep. 30, 2015
Net loss including noncontrolling interest	$ (559)	$ (4,136)	[1]	$ (1,130)		$ (6,239)	[1],[2]
Loss from discontinued operations	33	17	[1]	33		135	[1],[2]
Gain on divestitures	(5)	5	[1]	(21)		(204)	[1],[2]
Exploratory dry hole expense and unproved leasehold impairments				260		584	[2]
Depreciation, depletion, and amortization	648	872		1,995		2,492	[2]
Impairments	836	3,903	[1]	1,009		6,327	[1],[2]
Deferred income tax benefit	(529)	19	[1]	(755)		(1,299)	[1],[2]
Other Operating Activities, Cash Flow Statement				1		395
NET CASH PROVIDED BY CONTINUING OPERATING ACTIVITIES				1,634		2,380	[2]
NET CASH PROVIDED BY DISCONTINUED OPERATIONS				0		113	[2]
NET CASH PROVIDED BY OPERATING ACTIVITIES				1,634		2,493	[2]
Additions to oil and gas property				(1,281)		(3,562)	[2]
Net Cash Provided by (Used in) Investing Activities, Continuing Operations				(1,362)		(3,026)	[2]
NET CASH PROVIDED BY DISCONTINUED OPERATIONS				0		4,372	[2]
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES				(1,362)		1,346	[2]
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS				(237)		976	[2]
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR				1,467	[3]	679	[2]
CASH AND CASH EQUIVALENTS AT END OF PERIOD	1,230	1,655	[2]	1,230		1,655	[2]
Under Full Cost [Member]
Net loss including noncontrolling interest				(1,531)		(15,846)
Loss from discontinued operations						959
Gain on divestitures	(2)	0		(5)		0
Exploratory dry hole expense and unproved leasehold impairments				0		0
Depreciation, depletion, and amortization				3,138		21,753
Impairments		367		587		367
Deferred income tax benefit	(407)	(707)		(708)		(5,167)
Other Operating Activities, Cash Flow Statement				3		317
NET CASH PROVIDED BY CONTINUING OPERATING ACTIVITIES						2,572
NET CASH PROVIDED BY DISCONTINUED OPERATIONS						150
NET CASH PROVIDED BY OPERATING ACTIVITIES				1,759
Additions to oil and gas property				(1,406)		(3,844)
Net Cash Provided by (Used in) Investing Activities, Continuing Operations						(3,308)
NET CASH PROVIDED BY DISCONTINUED OPERATIONS						4,335
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES				(1,487)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS				(237)		886
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR				1,467		769
CASH AND CASH EQUIVALENTS AT END OF PERIOD	1,230	1,655		1,230		1,655
Change from Full Cost Method to Successful Efforts Method [Member] | Changes [Member]
Net loss including noncontrolling interest				401		9,607
Loss from discontinued operations						(824)
Gain on divestitures	(3)	5		(16)		(204)
Exploratory dry hole expense and unproved leasehold impairments				260		584
Depreciation, depletion, and amortization				(1,143)		(19,261)
Impairments		3,536		422		5,960
Deferred income tax benefit	(122)	726		(47)		3,868
Other Operating Activities, Cash Flow Statement				(2)		78
NET CASH PROVIDED BY CONTINUING OPERATING ACTIVITIES						(192)
NET CASH PROVIDED BY DISCONTINUED OPERATIONS						(37)
NET CASH PROVIDED BY OPERATING ACTIVITIES				(125)
Additions to oil and gas property				125		282
Net Cash Provided by (Used in) Investing Activities, Continuing Operations						282
NET CASH PROVIDED BY DISCONTINUED OPERATIONS						37
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES				125
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS				0		90
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR				0		(90)
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 0	$ 0		$ 0		$ 0

[1] Financial information for 2015 has been recast to reflect retrospective application of the successful efforts method of accounting. See Note 1.

[2] Financial information for 2015 has been recast to reflect retrospective application of the successful efforts method of accounting. See Note 1.

[3] Financial information for 2015 has been recast to reflect retrospective application of the successful efforts method of accounting. See Note 1.