ACCUMULATED OTHER COMPREHENSIVE LOSS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			$ 49	$ 39
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect	$ (254)		(254)
Union Carbide Corporation's stockholder's equity	1,739	$ 1,706	1,739	1,706	$ 1,368	$ 1,798
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			2	1
Other Comprehensive Income (Loss), Net of Tax	17	13	51	40
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Union Carbide Corporation's stockholder's equity	(1,555)	(1,280)	(1,555)	(1,280)	(1,352)	(1,320)
Other Comprehensive Income (Loss), Net of Tax			51	40
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	3
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect			0
Union Carbide Corporation's stockholder's equity	(57)	(58)	(57)	(58)	(59)	(62)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			2	1
Other Comprehensive Income (Loss), Net of Tax			2	4
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			49	36
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect			(254)
Union Carbide Corporation's stockholder's equity	(1,498)	(1,222)	(1,498)	(1,222)	$ (1,293)	$ (1,258)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			0	0
Other Comprehensive Income (Loss), Net of Tax			49	36
Other Comprehensive Income (Loss), Tax	(5)	(6)	(15)	(22)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	16	12	49	39
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cumulative translation adjustments
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	0	0	0	3
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	21	18	64	58
Reclassification from AOCI, Current Period, Tax	(5)	(6)	(15)	(22)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ 16	$ 12	$ 49	$ 36