Comprehensive Income (Loss) (Reclassification Out Of AOCI) (Details) - Reclassification Out Of Accumulated Other Comprehensive Income [Member] - USD ($) $ in Millions	1 Months Ended	2 Months Ended	3 Months Ended	4 Months Ended	6 Months Ended
	Apr. 30, 2021	Jun. 30, 2021	Jun. 30, 2022	Apr. 30, 2021	Jun. 30, 2022
Successor [Member] | OPEB [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax		$ 1			$ 6
Tax impact					(2)
Reclassifications, net of tax		1			4
Successor [Member] | OPEB [Member] | Amortization Of Defined Benefit Cost Items [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax		1	$ 3
Tax impact			(1)
Reclassifications, net of tax		1	2
Successor [Member] | OPEB [Member] | Prior-Service Credits (Costs) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax		$ 1	$ 3		$ 6
Predecessor [Member] | Pension [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax				$ (24)
Tax impact				5
Reclassifications, net of tax				(19)
Predecessor [Member] | Pension [Member] | Amortization Of Defined Benefit Cost Items [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax	$ (6)
Tax impact	1
Reclassifications, net of tax	(5)
Predecessor [Member] | Pension [Member] | Actuarial Gains (Losses) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax	(6)			(24)
Predecessor [Member] | OPEB [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax				5
Tax impact				(1)
Reclassifications, net of tax				4
Predecessor [Member] | OPEB [Member] | Amortization Of Defined Benefit Cost Items [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax	1
Reclassifications, net of tax	1
Predecessor [Member] | OPEB [Member] | Prior-Service Credits (Costs) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax	3			10
Predecessor [Member] | OPEB [Member] | Actuarial Gains (Losses) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax	$ (2)			$ (5)