Fresh Start Accounting (Reconciliation Of Enterprise Value To Estimated Fair Value) (Details) - Successor [Member] - USD ($) $ / shares in Units, $ in Millions	4 Months Ended	5 Months Ended
Apr. 30, 2021	Sep. 30, 2021
Fresh-Start Adjustment [Line Items]
Enterprise value		$ 12,500
Plus: Cash and cash equivalents and restricted cash		940
Less: Fair value of debt and other liabilities		(7,267)
Less: Pension and other postretirement benefits		(1,774)
Less: Deferred tax liability	$ (291)	(291)
Fair value of Successor stockholders' equity	$ 4,108	$ 4,108
Shares issued upon emergence	244,401,000	244,401,000
Per share value		$ 17

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