ACCUMULATED OTHER COMPREHENSIVE LOSS - Summary of Components of AOCI (Details) - USD ($) $ in Millions	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income
Accumulated other comprehensive loss	$ 655	$ 546	$ 1,136	$ 2,560	$ 2,688	$ 2,815
Foreign currency translation adjustment
Accumulated Other Comprehensive Income
Accumulated other comprehensive loss	(2,165)		(2,046)
Pension and postretirement benefit plan adjustments, net of income taxes
Accumulated Other Comprehensive Income
Accumulated other comprehensive loss	(42)		(40)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income
Accumulated other comprehensive loss	$ (2,207)	$ (2,223)	$ (2,086)	$ (2,156)	$ (2,061)	$ (2,137)