ACCUMULATED OTHER COMPREHENSIVE LOSS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ 15	$ 16
Accumulated Other Comprehensive Income (Loss) [Line Items]
Union Carbide Corporation's stockholder's equity	1,543	1,438	$ 1,915
Other Comprehensive Income (Loss), Net of Tax	15	16
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Union Carbide Corporation's stockholder's equity	(1,546)	(1,336)	(1,561)	$ (1,352)
Other Comprehensive Income (Loss), Net of Tax	15	16
Cumulative translation adjustments
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0
Accumulated Other Comprehensive Income (Loss) [Line Items]
Union Carbide Corporation's stockholder's equity	(57)	(59)	(57)	(59)
Other Comprehensive Income (Loss), Net of Tax	0	0
Pension and other postretirement benefits
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	15	16
Accumulated Other Comprehensive Income (Loss) [Line Items]
Union Carbide Corporation's stockholder's equity	(1,489)	(1,277)	$ (1,504)	$ (1,293)
Other Comprehensive Income (Loss), Net of Tax	15	16
Other Comprehensive Income (Loss), Tax	(4)	(6)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Pension and other postretirement benefits
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	19	22
Reclassification from AOCI, Current Period, Tax	(4)	(6)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ 15	$ 16