Comprehensive Income (Loss) (Reclassification Out Of AOCI) (Details) - Reclassification Out Of Accumulated Other Comprehensive Income [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Successor [Member] | OPEB [Member] | Amortization Of Defined Benefit Cost Items [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax	$ 3
Reclassifications, net of tax	3
Successor [Member] | OPEB [Member] | Prior-Service Credits (Costs) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax	$ 3
Predecessor [Member] | Pension [Member] | Amortization Of Defined Benefit Cost Items [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax		$ (18)
Tax impact		4
Reclassifications, net of tax		(14)
Predecessor [Member] | Pension [Member] | Actuarial Gains (Losses) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax		(18)
Predecessor [Member] | OPEB [Member] | Amortization Of Defined Benefit Cost Items [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax		4
Tax impact		(1)
Reclassifications, net of tax		3
Predecessor [Member] | OPEB [Member] | Prior-Service Credits (Costs) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax		7
Predecessor [Member] | OPEB [Member] | Actuarial Gains (Losses) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax		$ (3)