CONDENSED COMBINED DEBTOR-IN-POSSESSION FINANCIAL INFORMATION - Condensed Consolidating Debtors' Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2020		Jun. 30, 2020	[1]	Dec. 31, 2019		Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Assets [Abstract]
Total current assets	$ 420				$ 491
Total property, plant and equipment, net	4,360				6,352
Other assets	76				115
TOTAL ASSETS	4,856				6,958
Liabilities and Equity [Abstract]
Total current liabilities	1,194				709
Other long-term liabilities	727				720
Liabilities subject to compromise	4,516				0
Total equity	(2,273)	[1]	$ (2,376)		(296)	[1]	$ (208)	$ (279)	$ (247)
TOTAL LIABILITIES AND EQUITY	4,856				$ 6,958
Parent Company And Subsidiaries In Debtor In Possession Financing
Assets [Abstract]
Total current assets	379
Investments in subsidiaries	(261)
Total property, plant and equipment, net	3,937
Other assets	61
TOTAL ASSETS	4,116
Liabilities and Equity [Abstract]
Total current liabilities	1,217
Other long-term liabilities	724
Liabilities subject to compromise	4,516
Total equity	(2,341)
TOTAL LIABILITIES AND EQUITY	$ 4,116

[1] The above tables exclude amounts related to redeemable noncontrolling interests reported in mezzanine equity. See Note 7 Joint Ventures for more information about our noncontrolling interests and a settlement agreement entered into with one of our noncontrolling interest holders in the third quarter of 2020 where the modification of terms was treated as a return from noncontrolling interest holders.