Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Included in operating activities:
Interest paid, net of amounts capitalized		$ 190	$ 187
Income taxes paid to taxing authorities		151	298
Noncash investing activities:
Increase in asset retirement costs		40	12
Asset retirement obligations assumed by buyer(a)		1,082	$ 82
Capital expenditures incurred but not yet paid	$ 238	$ 302