Income Taxes - MEC - Net Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 68	$ 97
Additions based on tax positions related to the current year	10	15
Reductions based on tax positions related to the current year	(6)	(12)
Ending balance	73	68
Unrecognized tax benefits	88	79
MEC
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	16	13
Additions based on tax positions related to the current year	10	15
Interest	1	0
Reductions based on tax positions related to the current year	(5)	(12)
Ending balance	22	$ 16
Unrecognized tax benefits	$ 48