GOODWILL AND INTANGIBLE ASSETS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Goodwill and Intangible Assets
Goodwill	$ 950		$ 950
Intangible assets	42		43
Accumulated amortization	33		32
Amortization expense	1	$ 1
Expected amortization expense, year one	3
Expected amortization expense, year two	3
Expected amortization expense, year three	3
Expected amortization expense, year four	3
Expected amortization expense, year five	3
ITCTransmission
Goodwill and Intangible Assets
Goodwill	173		173
METC
Goodwill and Intangible Assets
Goodwill	454		454
Intangible assets	27		28
Accumulated amortization	32		31
ITC Midwest
Goodwill and Intangible Assets
Goodwill	323		323
ITC Great Plains
Goodwill and Intangible Assets
Intangible assets	15		15
Accumulated amortization	$ 1		$ 1