Basis of Presentation and Significant Accounting Policies, Voluntary Reorganization under Chapter 11 Cases - Schedule of Liabilities Subject to Compromise (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Liabilities subject to compromise, debt	$ 2,780	$ 0
Allowed claims, prepetition accounts payable and other	35
Total liabilities subject to compromise	2,932	$ 0
Senior Secured Notes
Debt Instrument [Line Items]
Liabilities subject to compromise, debt	2,092
Senior Unsecured Notes
Debt Instrument [Line Items]
Liabilities subject to compromise, debt	688
Senior Secured Term Loans and Senior Notes
Debt Instrument [Line Items]
Prepetition accrued interest on senior secured 1.5 lien and unsecured notes	$ 117