Comprehensive Income (Reclassification Out Of AOCI) (Details) - Reclassification Out Of Accumulated Other Comprehensive Income [Member] - USD ($) $ in Millions	4 Months Ended	8 Months Ended	12 Months Ended
	Apr. 30, 2021	Dec. 31, 2021	Dec. 31, 2023	Dec. 31, 2022
Pension [Member] | Amortization Of Defined Benefit Cost Items [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications of actuarial losses, pretax	$ (24)
Tax impact	5
Reclassifications, net of tax	(19)
OPEB [Member] | Amortization Of Defined Benefit Cost Items [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications of actuarial losses, pretax	5	$ 5	$ 22	$ 13
Tax impact	(1)	(1)	(5)	(2)
Reclassifications, net of tax	4	4	17	11
OPEB [Member] | Prior-Service Costs [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications of actuarial losses, pretax	10	$ 5	$ 22	$ 13
OPEB [Member] | Actuarial Losses [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications of actuarial losses, pretax	$ (5)