Discontinued Operations and Assets Held for Sale (Amounts Reported as Discontinued Operations in the Consolidated Statements of Comprehensive Earnings) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Upstream revenues	$ 92	$ 396
Marketing and midstream revenues		26
Total revenues	92	422
Production expenses	74	222
Exploration expenses		9
Marketing and midstream expenses		9
Depreciation, depletion and amortization		99
Asset impairments	179
Asset dispositions		1
General and administrative expenses	1	18
Financing costs, net	(2)	13
Restructuring and transaction costs		3
Other expenses	(3)	(22)
Total expenses	249	352
Earnings (loss) from discontinued operations before income taxes	(157)	70
Income tax expense (benefit)	(32)	9
Net earnings (loss) from discontinued operations, net of tax	(125)	61
Barnett Shale [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Upstream revenues	92	149
Total revenues	92	149
Production expenses	74	81
Depreciation, depletion and amortization		20
Asset impairments	179
Asset dispositions		1
Other expenses	(13)	6
Total expenses	240	108
Earnings (loss) from discontinued operations before income taxes	(148)	41
Income tax expense (benefit)	(32)	9
Net earnings (loss) from discontinued operations, net of tax	(116)	32
Canada [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Upstream revenues		247
Marketing and midstream revenues		26
Total revenues		273
Production expenses		141
Exploration expenses		9
Marketing and midstream expenses		9
Depreciation, depletion and amortization		79
General and administrative expenses	1	18
Financing costs, net	(2)	13
Restructuring and transaction costs		3
Other expenses	10	(28)
Total expenses	9	244
Earnings (loss) from discontinued operations before income taxes	(9)	29
Net earnings (loss) from discontinued operations, net of tax	$ (9)	$ 29