Income Taxes - MEC - Net Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 153	$ 145
Additions based on tax positions related to the current year	24	19
Reductions based on tax positions related to the current year	(19)	(14)
Reductions for tax positions of prior years	(83)	(1)
Ending balance	97	153
Unrecognized tax benefits	100	141
MEC
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	8	8
Additions based on tax positions related to the current year	16	4
Reductions based on tax positions related to the current year	(11)	(3)
Reductions for tax positions of prior years	0	(1)
Ending balance	13	$ 8
Unrecognized tax benefits	$ 33