Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Supplemental Cash Flow Elements [Abstract]
Proceeds from Income Tax Refunds	$ 3	$ 5
Included in operating activities:
Interest paid, net of amounts capitalized	52	52
Income taxes paid to taxing authorities, net of refunds received (a)	(5)	(29)
Noncash investing activities:
Increase (decrease) in asset retirement costs	(8)	23
Asset retirement obligations assumed by buyer (b)	0	98
Capital expenditures incurred but not yet paid	$ 238	$ 250