Chapter 11 Proceedings and Ability to continue as a Going Concern - Liabilities Subject to Compromise (Details) - USD ($) $ in Millions	5 Months Ended
	Dec. 13, 2019	Dec. 12, 2019
Debt Instrument [Line Items]
Liabilities Subject to Compromise		$ 7,600
Liabilities Subject To Compromise, Accrued Interest		207
Liabilities Subject to Compromise, Debt and Accrued Interest		7,634
Contractual interest expense on Notes in excess of recorded interest expense	$ 257
Senior Notes [Member] | Senior Notes, 5.125% due 2020
Debt Instrument [Line Items]
Liabilities Subject To Compromise, Debt		365
Senior Notes [Member] | Exchangeable Senior Notes, 5.875 Percent due 2021
Debt Instrument [Line Items]
Liabilities Subject To Compromise, Debt		1,265
Senior Notes [Member] | Senior Notes, 7.75 Percent due 2021
Debt Instrument [Line Items]
Liabilities Subject To Compromise, Debt		750
Senior Notes [Member] | Senior Notes, 4.50% due 2022
Debt Instrument [Line Items]
Liabilities Subject To Compromise, Debt		646
Senior Notes [Member] | Senior Notes, 8.25 Percent due 2023
Debt Instrument [Line Items]
Liabilities Subject To Compromise, Debt		750
Senior Notes [Member] | Senior Notes, 9.875 Percent due 2024
Debt Instrument [Line Items]
Liabilities Subject To Compromise, Debt		790
Senior Notes [Member] | Senior Notes, 9.875 Percent due 2025
Debt Instrument [Line Items]
Liabilities Subject To Compromise, Debt		600
Senior Notes [Member] | Senior Notes, 6.50% due 2036
Debt Instrument [Line Items]
Liabilities Subject To Compromise, Debt		453
Senior Notes [Member] | Senior Notes, 6.80% due 2037
Debt Instrument [Line Items]
Liabilities Subject To Compromise, Debt		259
Senior Notes [Member] | Senior Notes, 7.00% due 2038
Debt Instrument [Line Items]
Liabilities Subject To Compromise, Debt		461
Senior Notes [Member] | Senior Notes, 9.875% due 2039
Debt Instrument [Line Items]
Liabilities Subject To Compromise, Debt		250
Senior Notes [Member] | Senior Notes, 6.75% due 2040
Debt Instrument [Line Items]
Liabilities Subject To Compromise, Debt		463
Senior Notes [Member] | Senior Notes, 5.95% due 2042
Debt Instrument [Line Items]
Liabilities Subject To Compromise, Debt		$ 375