Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Common stock issuances
Balance at the beginning of the year (in shares)			895,115,637
Balance at the end of the year (in shares)	1,043,640,621		1,043,640,621
Basic earnings (loss) per common share
Net income (loss) attributable to common stockholders	$ (912)	$ 1,869	$ 354	$ 3,425
Less: Net income allocated to participating securities	0	8	1	16
Net income (loss), net of participating securities	$ (912)	$ 1,861	$ 353	$ 3,409
Weighted average number of basic shares (in shares)	845,700,000	761,700,000	781,100,000	764,300,000
Net income (loss) attributable to common stockholders per share—basic (in usd per share)	$ (1.08)	$ 2.44	$ 0.45	$ 4.46
Diluted earnings (loss) per common share
Net income (loss), net of participating securities	$ (912)	$ 1,861	$ 353	$ 3,409
Weighted average number of basic shares (in shares)	845,700,000	761,700,000	781,100,000	764,300,000
Dilutive securities (in shares)	0	1,600,000	1,100,000	1,500,000
Total diluted weighted average common shares (in shares)	845,700,000	763,300,000	782,200,000	765,800,000
Net income (loss) attributable to common stockholders per share—diluted (in usd per share)	$ (1.08)	$ 2.44	$ 0.45	$ 4.45
Accumulated other comprehensive loss
Beginning balance	$ 21,347	$ 20,931	$ 21,330	$ 20,572
Other comprehensive loss, before reclassifications			(160)
Ending balance	41,005	21,488	$ 41,005	21,488
Anadarko
Common stock issuances
Treasury stock (in shares)			2,000,000
Common Stock
Common stock issuances
Issued in the ordinary course (in shares)			2,394,000
Issued as part of the Merger (in shares)			146,131,000
Accumulated other comprehensive loss
Beginning balance	179	179	$ 179	179
Ending balance	209	179	209	179
Gains and (losses) on derivatives
Accumulated other comprehensive loss
Beginning balance			5
Other comprehensive loss, before reclassifications			(130)
Ending balance	(125)		(125)
Pension and postretirement benefit plans
Accumulated other comprehensive loss
Beginning balance			(170)
Other comprehensive loss, before reclassifications			(30)
Ending balance	(200)		(200)
Foreign currency translation adjustments
Accumulated other comprehensive loss
Beginning balance			(7)
Other comprehensive loss, before reclassifications			0
Ending balance	(7)		(7)
Accumulated Other Comprehensive Loss
Accumulated other comprehensive loss
Beginning balance	(184)	(308)	(172)	(258)
Ending balance	$ (332)	$ (155)	$ (332)	$ (155)