Change in Accounting Principle - Statement of Consolidated Cash Flow (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Net loss including noncontrolling interest	$ (200)	$ (797)	$ (571)	$ (2,103)
Loss from discontinued operations	0	(120)	0	118
Gain on divestitures	(17)	(227)	(16)	(209)
Exploratory dry hole expense and unproved leasehold impairments			139	385
Depreciation, depletion, and amortization	669	794	1,347	1,620
Impairments	173	512	173	2,424
Provision (benefit) from deferred income taxes	(225)	(169)	(226)	(1,318)
NET CASH PROVIDED BY CONTINUING OPERATING ACTIVITIES			983	1,623
NET CASH PROVIDED BY DISCONTINUED OPERATIONS			0	159
NET CASH PROVIDED BY OPERATING ACTIVITIES			983	1,782
Additions to oil and gas property			(925)	(2,783)
Net Cash Provided by (Used in) Investing Activities, Continuing Operations			(966)	(2,099)
NET CASH PROVIDED BY DISCONTINUED OPERATIONS			0	4,372
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES			(966)	2,273
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS			(266)	2,271
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR			1,467	679
CASH AND CASH EQUIVALENTS AT END OF PERIOD	1,201	2,950	1,201	2,950
Change from Full Cost Method to Successful Efforts Method [Member]
Net loss including noncontrolling interest			(571)	(2,103)
Loss from discontinued operations				118
Gain on divestitures	(17)	(227)	(16)	(209)
Exploratory dry hole expense and unproved leasehold impairments			139	385
Depreciation, depletion, and amortization			1,347	1,620
Impairments		512	173	2,424
Provision (benefit) from deferred income taxes	(225)	(169)	(226)	(1,318)
Other Operating Activities, Cash Flow Statement			(30)	608
NET CASH PROVIDED BY CONTINUING OPERATING ACTIVITIES				1,623
NET CASH PROVIDED BY DISCONTINUED OPERATIONS				159
NET CASH PROVIDED BY OPERATING ACTIVITIES			983
Additions to oil and gas property			(925)	(2,783)
Net Cash Provided by (Used in) Investing Activities, Continuing Operations				(2,099)
NET CASH PROVIDED BY DISCONTINUED OPERATIONS				4,372
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES			(966)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS			(266)	2,271
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR			1,467	679
CASH AND CASH EQUIVALENTS AT END OF PERIOD	1,201	2,950	1,201	2,950
Change from Full Cost Method to Successful Efforts Method [Member] | Under Full Cost [Member]
Net loss including noncontrolling interest			(1,183)	(10,200)
Loss from discontinued operations				864
Gain on divestitures	(5)	0	(3)	0
Exploratory dry hole expense and unproved leasehold impairments			0	0
Depreciation, depletion, and amortization			2,300	15,124
Impairments		0	105	0
Provision (benefit) from deferred income taxes	(120)	(1,525)	(301)	(4,460)
Other Operating Activities, Cash Flow Statement			(28)	311
NET CASH PROVIDED BY CONTINUING OPERATING ACTIVITIES				1,737
NET CASH PROVIDED BY DISCONTINUED OPERATIONS				196
NET CASH PROVIDED BY OPERATING ACTIVITIES			1,057
Additions to oil and gas property			(999)	(2,987)
Net Cash Provided by (Used in) Investing Activities, Continuing Operations				(2,303)
NET CASH PROVIDED BY DISCONTINUED OPERATIONS				4,335
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES			(1,040)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS			(266)	2,181
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR			1,467	769
CASH AND CASH EQUIVALENTS AT END OF PERIOD	1,201	2,950	1,201	2,950
Change from Full Cost Method to Successful Efforts Method [Member] | Changes [Member]
Net loss including noncontrolling interest			612	8,097
Loss from discontinued operations				(746)
Gain on divestitures	(12)	(227)	(13)	(209)
Exploratory dry hole expense and unproved leasehold impairments			139	385
Depreciation, depletion, and amortization			(953)	(13,504)
Impairments		512	68	2,424
Provision (benefit) from deferred income taxes	(105)	1,356	75	3,142
Other Operating Activities, Cash Flow Statement			(2)	297
NET CASH PROVIDED BY CONTINUING OPERATING ACTIVITIES				(114)
NET CASH PROVIDED BY DISCONTINUED OPERATIONS				(37)
NET CASH PROVIDED BY OPERATING ACTIVITIES			(74)
Additions to oil and gas property			74	204
Net Cash Provided by (Used in) Investing Activities, Continuing Operations				204
NET CASH PROVIDED BY DISCONTINUED OPERATIONS				37
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES			74
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