Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues and other income:
Revenues from contracts with customers	$ 1,537	$ 873
Net gain (loss) on commodity derivatives	(102)	81
Marketing revenues	0	34
Income from equity method investments	37	69
Net gain (loss) on disposal of assets	257	1
Other income	4	14
Total revenues and other income	1,733	1,072
Costs and expenses:
Production	217	153
Marketing, including purchases from related parties	0	34
Other operating	130	89
Exploration Expense	52	28
Depreciation, depletion and amortization	590	556
Impairments	8	4
Taxes other than income	64	39
General and administrative	100	97
Total costs and expenses	1,161	1,000
Income (loss) from operations	572	72
Net interest and other	(45)	(78)
Other net periodic benefit costs	(3)	(10)
Income (loss) from continuing operations before income taxes	524	(16)
Provision (benefit) for income taxes	168	34
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	356	(50)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0	(4,907)
Net income (loss)	$ 356	$ (4,957)
Earnings Per Share, Basic [Abstract]
Income (loss) from continuing operations, per basic share	$ 0.42	$ (0.06)
Income (loss) from discontinued operations, per basic share	0.00	(5.78)
Net income (loss), per basic share	0.42	(5.84)
Earnings Per Share, Diluted [Abstract]
Income (loss) from continuing operations, per diluted share	0.42	(0.06)
Income (loss) from discontinued operations, per diluted share	0.00	(5.78)
Net income (loss), per diluted share	0.42	(5.84)
Dividends paid, per share	$ 0.05	$ 0.05
Weighted average common shares outstanding:
Weighted average common shares outstanding, basic	851	849
Weighted average common shares outstanding, diluted	852	849