CONDENSED FINANCIAL INFORMATION OF PARENT - Basis Of Presentation (Details) - USD ($)		12 Months Ended
	Oct. 20, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Net Income		$ (539,000,000)	$ (643,000,000)	$ (590,000,000)
Decrease in retained earnings		$ (1,666,000,000)	(1,634,000,000)
Correction
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Net Income			33,000,000	8,000,000
Decrease in retained earnings			$ 47,000,000	$ 6,000,000
NM Green Holdings, Inc.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Merger agreement, share price (in dollars per share)	$ 50.30
Merger agreement term, ownership percentage benchmark	15.00%
Merger agreement, termination rights term, extension period	3 months
Merger agreement, termination rights term, termination fees	$ 130,000,000
Merger agreement, termination rights term, termination fees as remedy	184,000,000
Merger agreement, termination rights term, termination fees, out-of-pocket fees and expenses reimbursable limit (up to)	$ 10,000,000