SEGMENT INFORMATION (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
OPERATING REVENUES:
Operating revenues		$ 303	$ 298	$ 601	$ 578
INCOME (LOSS) BEFORE INCOME TAXES:
Income before income taxes		129	116	256	220
NET INCOME:
NET INCOME		81	74	161	139
TOTAL ASSETS:
Assets		8,607		8,607		$ 8,223
Regulated operations
OPERATING REVENUES:
Operating revenues		310	298	615	578
INCOME (LOSS) BEFORE INCOME TAXES:
Income before income taxes		164	167	326	319
NET INCOME:
NET INCOME		101	103	200	197
TOTAL ASSETS:
Assets		8,531		8,531		8,162
ITC Holdings and other
OPERATING REVENUES:
Operating revenues		0	0	0	0
INCOME (LOSS) BEFORE INCOME TAXES:
Income before income taxes		(35)	(51)	(70)	(99)
NET INCOME:
NET INCOME		81	74	161	139
TOTAL ASSETS:
Assets		4,666		4,666		4,503
Intercompany eliminations
OPERATING REVENUES:
Operating revenues		(7)	0	(14)	0
NET INCOME:
NET INCOME		(101)	$ (103)	(200)	$ (197)
TOTAL ASSETS:
Assets	[1]	$ (4,590)		$ (4,590)		$ (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