SEGMENT INFORMATION (Details) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
OPERATING REVENUES:
Operating revenues		$ 342		$ 320		$ 664	$ 627
INCOME (LOSS) BEFORE INCOME TAXES:
Income before income taxes		161		116		285	231
NET INCOME:
NET INCOME		121	$ 92	87	$ 84	213	171
TOTAL ASSETS:
Assets		10,463				10,463		$ 10,058
Regulated Operating Subsidiaries
OPERATING REVENUES:
Operating revenues		350		324		681	641
INCOME (LOSS) BEFORE INCOME TAXES:
Income before income taxes		194		155		351	306
NET INCOME:
NET INCOME		142		115		258	226
TOTAL ASSETS:
Assets		10,269				10,269		9,946
ITC Holdings and other
INCOME (LOSS) BEFORE INCOME TAXES:
Income before income taxes		(33)		(39)		(66)	(75)
NET INCOME:
NET INCOME		121		87		213	171
TOTAL ASSETS:
Assets		5,666				5,666		5,402
Intercompany eliminations
OPERATING REVENUES:
Operating revenues		(8)		(4)		(17)	(14)
NET INCOME:
NET INCOME		(142)		$ (115)		(258)	$ (226)
TOTAL ASSETS:
Assets	[1]	$ (5,472)				$ (5,472)		$ (5,290)

[1] Reconciliation of total assets results primarily from differences in the netting of deferred tax assets and liabilities in our segments as compared to the classification in our condensed consolidated statements of financial position