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, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Fresh Start Accounting [Abstract]
Enterprise value	$ 12,500			$ 12,500
Plus: Cash and cash equivalents and restricted cash	940	$ 1,239	$ 322	$ 2,178	$ 1,887
Less: Fair value of debt and other liabilities	(7,267)
Less: Pension and other postretirement benefits	(1,774)
Less: Deferred tax liability	(291)	(643)	(558)
Fair value of Successor stockholders' equity	$ 4,108	$ 5,279	$ 5,134
Shares issued upon emergence	244,401,000
Per share value	$ 17