Supplemental Cash Flow Disclosures - MEC (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Income Statements, Captions [Line Items]
Cash and cash equivalents	$ 1,096	$ 1,290
Restricted cash and cash equivalents	127	140
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
MEC
Condensed Income Statements, Captions [Line Items]
Cash and cash equivalents	232	38
Restricted cash and cash equivalents	7	7
Total cash and cash equivalents and restricted cash and cash equivalents	239	45	330	$ 56
Interest paid, net of amounts capitalized	279	286	224
Income taxes received, net	746	709	450
Accrued capital expenditures	$ 257	$ 227	$ 337