Comprehensive Income (Loss) (Accumulated Other Comprehensive Income (Loss), Net Of Tax) (Details) - USD ($) $ in Millions	4 Months Ended	8 Months Ended	12 Months Ended
	Apr. 30, 2021	Dec. 31, 2021	Dec. 31, 2022	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning	$ (4,900)	$ 4,108	$ 4,600	$ (4,394)
Net current-period other comprehensive income (loss)	359	60	19	(105)
Balance at ending	4,108	4,600	5,134	(4,900)
Pension And OPEB [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Deferred tax items		15	23	234	$ 204
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning	(755)		60	(650)
Other comprehensive income (loss) before reclassifications	344	64	30	(396)
Amounts reclassified from accumulated other comprehensive income (loss) to net loss	15	(4)	(11)	291
Net current-period other comprehensive income (loss)	359	60	19	(105)
Cancellation of Predecessor equity	(396)
Balance at ending		60	79	(755)
Accumulated Other Comprehensive Income (Loss) [Member] | Pension [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning	(699)			(684)
Other comprehensive income (loss) before reclassifications	270			(320)
Amounts reclassified from accumulated other comprehensive income (loss) to net loss	19			305
Net current-period other comprehensive income (loss)	289			(15)
Cancellation of Predecessor equity	(410)
Balance at ending				(699)
Accumulated Other Comprehensive Income (Loss) [Member] | OPEB [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning	(56)		60	34
Other comprehensive income (loss) before reclassifications	74	64	30	(76)
Amounts reclassified from accumulated other comprehensive income (loss) to net loss	(4)	(4)	(11)	(14)
Net current-period other comprehensive income (loss)	70	60	19	(90)
Cancellation of Predecessor equity	$ 14
Balance at ending		$ 60	$ 79	$ (56)