SEGMENT INFORMATION (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
OPERATING REVENUES:
Operating revenues		$ 299	$ 254	$ 900	$ 832
INCOME (LOSS) BEFORE INCOME TAXES:
Income before income taxes		128	79	384	299
NET INCOME:
NET INCOME		82	51	243	190
TOTAL ASSETS:
Assets		8,727		8,727		$ 8,223
Regulated operations
OPERATING REVENUES:
Operating revenues		306	261	921	839
INCOME (LOSS) BEFORE INCOME TAXES:
Income before income taxes		166	120	492	439
NET INCOME:
NET INCOME		104	75	304	272
TOTAL ASSETS:
Assets		8,649		8,649		8,162
ITC Holdings and other
OPERATING REVENUES:
Operating revenues		1	0	1	1
INCOME (LOSS) BEFORE INCOME TAXES:
Income before income taxes		(38)	(41)	(108)	(140)
NET INCOME:
NET INCOME		82	51	243	190
TOTAL ASSETS:
Assets		4,683		4,683		4,503
Intercompany eliminations
OPERATING REVENUES:
Operating revenues		(8)	(7)	(22)	(8)
NET INCOME:
NET INCOME		(104)	$ (75)	(304)	$ (272)
TOTAL ASSETS:
Assets	[1]	$ (4,605)		$ (4,605)		$ (4,442)

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