Fresh Start Accounting (Fresh Start - Disposition Of Liabilities Subject To Compromise) (Details) - USD ($) $ in Millions	Apr. 30, 2021	Dec. 31, 2020
Liabilities subject to compromise pre-emergence		$ (11,565)
Reinstated on the Effective Date:
Accounts payable		(57)
Other current liabilities		$ (62)
Reorganization Adjustments [Member]
Liabilities subject to compromise pre-emergence	$ 11,570
Reinstated on the Effective Date:
Accounts payable	(66)
Other current liabilities	(59)
Less: total liabilities reinstated	(125)
Amounts settled per the Plan of Reorganization
Issuance of take back debt	(750)
Payment for settlement of unsecured senior noteholders	(1,313)
Equity issued at emergence to unsecured senior noteholders	(4,108)
Total amounts settled	(6,171)
Gain on settlement of Liabilities Subject to Compromise	$ 5,274