Employee Retirement Benefits - Unrecognized Amounts (Details) - Pension Benefits [Member] - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Components of AOCI:
Unrecognized prior service benefit	$ 2	$ 1
Unrecognized losses	(73)	(91)
Total	(71)	(90)
Tax effects on components of AOCI [Abstract]
Tax expense (benefit) related to unrecognized prior service benefit (cost)	1	0
Tax expense (benefit) related to unrecognized gain (loss)	(22)	(33)
Unrecognized amounts included in regulatory assets (liabilities) [Abstract]
Unrecognized prior service cost	0	2
Unrecognized losses	221	277
Total	$ 221	$ 279