ORGANIZATION AND BASIS OF PRESENTATION - Accounts Receivable (Details) - USD ($) $ in Millions		12 Months Ended
	Feb. 27, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Deferred for recovery		$ 103	$ 25	$ 24
Customer Receivables
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		46	50	49
Charged to income		174	81	77
Charged to other accounts		46	47	60
Write-offs		(102)	(132)	(136)
Ending balance		164	46	50
Other Receivables
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		21	2	1
Charged to income		7	27	13
Charged to other accounts		10	1	0
Write-offs		(12)	(9)	(12)
Ending balance		26	21	2
Affiliated companies
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance		1,063	920	0
Charged to income		0	143	920
Charged to other accounts		0	0	0
Write-offs		(1,063)	0	0
Ending balance		$ 0	$ 1,063	$ 920
Affiliated companies | FES
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Write-offs	$ (1,100)