CREDIT LOSSES - Changes in Allowance for Credit Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 9
Provision for expected credit losses	1	$ 2	$ 2
Write-offs charged against the allowance	(2)
Ending balance	$ 8	$ 9