Comprehensive Income (Loss) (Accumulated Other Comprehensive Income (Loss), Net Of Tax) (Details) - USD ($) $ in Millions	1 Months Ended	2 Months Ended	3 Months Ended					4 Months Ended	5 Months Ended	9 Months Ended
	Apr. 30, 2021	Jun. 30, 2021	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Mar. 31, 2021	Apr. 30, 2021	Sep. 30, 2021	Sep. 30, 2022	Jan. 01, 2022	Jan. 31, 2021
Successor [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning		$ 4,108	$ 4,796	$ 4,678	$ 4,600	$ 4,248			$ 4,108	$ 4,600
Net current-period other comprehensive income (loss)		41	(2)	4	(2)	3			44
Balance at ending	$ 4,108	4,248	4,933	4,796	4,678	4,385		$ 4,108	4,385	4,933
Successor [Member] | Pension And OPEB [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax			16							16
Successor [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning			62	58	60	41				60
Other comprehensive income (loss) before reclassifications									46	8
Amounts reclassified from accumulated other comprehensive income (loss) to net loss									(2)	(8)
Net current-period other comprehensive income (loss)		41	(2)	4	(2)	3			44
Balance at ending		41	60	$ 62	58	44			44	60
Successor [Member] | Accumulated Other Comprehensive Income (Loss) [Member] | OPEB [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning					$ 60					60
Other comprehensive income (loss) before reclassifications									46	8
Amounts reclassified from accumulated other comprehensive income (loss) to net loss									(2)	(8)
Net current-period other comprehensive income (loss)									44
Balance at ending			$ 60			44			44	$ 60
Predecessor [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning	(4,830)	$ 4,108					$ (4,900)	(4,900)	4,108
Net current-period other comprehensive income (loss)	348						11	359
Balance at ending	4,108						(4,830)	4,108
Predecessor [Member] | Pension And OPEB [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax						$ 12			$ 12		$ 15	$ 234
Predecessor [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning	(744)						(755)	(755)
Other comprehensive income (loss) before reclassifications								344
Amounts reclassified from accumulated other comprehensive income (loss) to net loss								15
Net current-period other comprehensive income (loss)	$ 348						11	359
Cancellation of Predecessor equity								396
Balance at ending							(744)
Predecessor [Member] | Accumulated Other Comprehensive Income (Loss) [Member] | Pension [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning							(699)	(699)
Other comprehensive income (loss) 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
Predecessor [Member] | Accumulated Other Comprehensive Income (Loss) [Member] | OPEB [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning							$ (56)	(56)
Other comprehensive income (loss) before reclassifications								74
Amounts reclassified from accumulated other comprehensive income (loss) to net loss								(4)
Net current-period other comprehensive income (loss)								70
Cancellation of Predecessor equity								$ (14)