Changes in Accounting Principle - Consolidated Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Net earnings (loss)		$ 1,078	$ (1,458)	[1]	$ (13,645)	[1]
Depreciation, depletion and amortization		2,074	2,096	[1]	4,022	[1]
Exploratory dry hole expense and unproved leasehold impairments		219	113	[1]	248	[1]
Asset impairments		17	1,310	[1]	17,647	[1]
Gains and losses on asset sales		(217)	(1,483)	[1]	7	[1]
Deferred income tax expense (benefit)		(294)	41	[1]	(5,976)	[1]
Share-based compensation		198	233	[1]	244	[1]
Other		(122)	270	[1]	312	[1]
Net cash from operating activities		2,909	1,500	[1]	4,898	[1]
Capital expenditures		(2,759)	(2,047)	[1]	(4,787)	[1]
Divestitures of property and equipment		417	3,113	[1]	107	[1]
Net cash from investing activities		(2,210)	(594)	[1]	(5,803)	[1]
Under Full Cost [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Net earnings (loss)	$ 594
Depreciation, depletion and amortization	417
Gains and losses on asset sales	1
Deferred income tax expense (benefit)	(232)
Share-based compensation	36
Other	26
Net cash from operating activities	796
Capital expenditures	(871)
Divestitures of property and equipment	102
Net cash from investing activities	(783)
Changes [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Net earnings (loss)	(290)
Depreciation, depletion and amortization	111
Exploratory dry hole expense and unproved leasehold impairments	139
Gains and losses on asset sales	(19)
Deferred income tax expense (benefit)	(13)
Share-based compensation	11
Other	(10)
Net cash from operating activities	(71)
Capital expenditures	72
Divestitures of property and equipment	(1)
Net cash from investing activities	$ 71
Change from Full Cost Method to Successful Efforts Method [Member] | Under Full Cost [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Net earnings (loss)		1,871	(3,704)		(15,203)
Depreciation, depletion and amortization		1,579	1,792		3,129
Asset impairments			4,975		20,820
Gains and losses on asset sales		(5)	(1,887)
Deferred income tax expense (benefit)		(252)	(273)		(5,828)
Share-based compensation		158	194		181
Other		(108)	303		281
Net cash from operating activities		3,216	1,778		5,419
Capital expenditures		(3,074)	(2,330)		(5,308)
Divestitures of property and equipment		425	3,118
Net cash from investing activities		(2,517)	(872)		(6,324)
Change from Full Cost Method to Successful Efforts Method [Member] | Changes [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Net earnings (loss)		(793)	2,246		1,558
Depreciation, depletion and amortization		495	304		893
Exploratory dry hole expense and unproved leasehold impairments		219	113		248
Asset impairments			(3,665)		(3,173)
Gains and losses on asset sales		(212)	404		7
Deferred income tax expense (benefit)		(42)	314		(148)
Share-based compensation		40	39		63
Other		(14)	(33)		31
Net cash from operating activities		(307)	(278)		(521)
Capital expenditures		315	283		521
Divestitures of property and equipment		(8)	(5)
Net cash from investing activities		$ 307	$ 278		$ 521

[1] Prior year amounts have been recast due to change in accounting principle. See Note 2 in “Item 8. Financial Statements and Supplementary Data” of this report.