Comprehensive Income (Accumulated Other Comprehensive Income, Net Of Tax) (Details) - USD ($) $ in Millions	4 Months Ended	8 Months Ended	12 Months Ended
	Apr. 30, 2021	Dec. 31, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning	$ (4,900)	$ 4,108	$ 5,134	$ 4,600
Net current-period other comprehensive income (loss)	359	60	17	19
Balance at ending	4,108	4,600	5,279	5,134
Pension And OPEB [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Deferred tax items		15	29	23	$ 234
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning	(755)		79	60
Other comprehensive income before reclassifications	344	64		30
Amounts reclassified from accumulated other comprehensive income (loss) to net loss	15	(4)	(17)	(11)
Net current-period other comprehensive income (loss)	359	60	17	19
Cancellation of Predecessor equity	(396)
Balance at ending		60	96	79
Accumulated Other Comprehensive Income (Loss) [Member] | Pension [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning	(699)
Other comprehensive income before reclassifications	270
Amounts reclassified from accumulated other comprehensive income (loss) to net loss	19
Net current-period other comprehensive income (loss)	289
Cancellation of Predecessor equity	(410)
Accumulated Other Comprehensive Income (Loss) [Member] | OPEB [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning	(56)		79	60
Other comprehensive income before reclassifications	74	64	34	30
Amounts reclassified from accumulated other comprehensive income (loss) to net loss	(4)	(4)	(17)	(11)
Net current-period other comprehensive income (loss)	70	60	17	19
Cancellation of Predecessor equity	$ 14
Balance at ending		$ 60	$ 96	$ 79