Fresh Start Accounting - Reorganization Items, Net (Details) - USD ($) $ in Millions		1 Months Ended	2 Months Ended	3 Months Ended
	Feb. 09, 2021	Feb. 09, 2021	Mar. 31, 2021	Mar. 31, 2020
Reorganizations [Abstract]
Gains on the settlement of liabilities subject to compromise		$ 6,443
Accrual for allowed claims		(1,002)
Gain on fresh start adjustments		201
Gain from release of commitment liabilities		55
Professional service provider fees and other		(60)
Success fees for professional service providers		(38)
Surrender of other receivable	$ (18)	(18)
FLLO alternative transaction fee		(12)
Total reorganization items, net	$ (6,370)	$ 5,569	$ 0	$ 0