Supplemental Cash Flow Disclosures - PAC (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	$ 1,096	$ 1,290
Restricted cash and cash equivalents	127	140
Investments and restricted cash and cash equivalents and investments	21	15
Total cash and cash equivalents and restricted cash and cash equivalents	1,244	1,445	$ 1,268	$ 883
Interest paid, net of amounts capitalized	2,041	1,855	1,723
Income taxes received, net	(1,309)	(1,361)	(850)
Accrued capital expenditures	834	801	888
PAC
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	179	13
Restricted cash and cash equivalents	4	4
Investments and restricted cash and cash equivalents and investments	3	2
Total cash and cash equivalents and restricted cash and cash equivalents	186	19	36	$ 92
Interest paid, net of amounts capitalized	395	348	340
Income taxes received, net	(120)	107	171
Accrued capital expenditures	$ 254	$ 344	$ 293