Employee Benefits - Change in Plan Assets Measured at Fair Value (Details) - Combined Pension Plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Change in plan assets
Fair value of plan assets at beginning of year	$ 4,715	$ 8,531
Fair value of plan assets at end of year	4,476	4,715
Level 3
Change in plan assets
Fair value of plan assets at beginning of year	5	11
Dispositions	(2)	(5)
Actual return on plan assets	2	(1)
Fair value of plan assets at end of year	5	5
Level 3 | High Yield Bonds
Change in plan assets
Fair value of plan assets at beginning of year	4	6
Dispositions	(2)	(1)
Actual return on plan assets	2	(1)
Fair value of plan assets at end of year	4	4
Level 3 | U.S. Stocks
Change in plan assets
Fair value of plan assets at beginning of year	1	5
Dispositions	0	(4)
Actual return on plan assets	0	0
Fair value of plan assets at end of year	$ 1	$ 1