SUPPLEMENTAL FINANCIAL INFORMATION - Allowance for Doubtful Accounts (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at beginning of period	$ 117	$ 120	$ 125	$ 112
Adoption of new accounting standard	0	0	0	4
Charged to costs and expenses	2	3	(1)	15
Write-offs	(2)	(3)	(3)	(4)
Currency translation adjustments	(2)	2	(6)	(5)
Balance at end of period	$ 115	$ 122	$ 115	$ 122