Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Included in operating activities:
Interest paid, net of amounts capitalized	$ 52	$ 52
Income taxes paid to taxing authorities	29	231
Noncash investing activities:
Increase in asset retirement costs	23	4
Asset retirement obligations assumed by buyer(a)	98	1
Capital expenditures incurred but not yet paid	$ 250	$ 279