Fresh Start Accounting (Reconciliation Of Enterprise Value To Estimated Fair Value) (Details) - USD ($) $ / shares in Units, $ in Millions	4 Months Ended
	Apr. 30, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fresh Start Accounting [Abstract]
Enterprise value	$ 12,500		$ 12,500
Plus: Cash and cash equivalents and restricted cash	940	$ 322	2,178	$ 1,887	$ 810
Less: Fair value of debt and other liabilities	(7,267)
Less: Pension and other postretirement benefits	(1,774)
Less: Deferred tax liability	(291)	(558)	(387)
Fair value of Successor stockholders' equity	$ 4,108	$ 5,134	$ 4,600
Shares issued upon emergence	244,401,000
Per share value	$ 17