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	6 Months Ended
	Apr. 30, 2021	Jun. 30, 2021	Jun. 30, 2022	Mar. 31, 2022	Mar. 31, 2021	Apr. 30, 2021	Jun. 30, 2022	Jan. 01, 2022	Jan. 01, 2021
Successor [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning		$ 4,108	$ 4,678	$ 4,600			$ 4,600
Net current-period other comprehensive income (loss)		41	4	(2)			2
Balance at ending	$ 4,108	4,248	4,796	4,678		$ 4,108	4,796
Successor [Member] | Pension And OPEB [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax			17				17
Successor [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning			58	60			60
Other comprehensive income (loss) before reclassifications		42					6
Amounts reclassified from accumulated other comprehensive income (loss) to net loss		(1)					(4)
Net current-period other comprehensive income (loss)		41	4	(2)			2
Balance at ending		41	62	58			62
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		42					6
Amounts reclassified from accumulated other comprehensive income (loss) to net loss		(1)					(4)
Net current-period other comprehensive income (loss)		41					2
Balance at ending		41	$ 62				$ 62
Predecessor [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning	(4,830)	4,108			$ (4,900)	(4,900)
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		$ 14						$ 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)