DEBT Additional Information (Details) (USD $)	9 Months Ended								0 Months Ended							0 Months Ended			0 Months Ended		0 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 ITC Holdings		Sep. 30, 2013 ITC Holdings 2013 Term Loan Credit Agreement Unsecured Debt	Feb. 15, 2013 ITC Holdings 2013 Term Loan Credit Agreement Unsecured Debt	Jul. 03, 2013 ITC Holdings Senior Notes, due July 1, 2023 Unsecured Debt	Jul. 03, 2013 ITC Holdings Senior Notes, due July 1, 2043 Unsecured Debt	Jul. 03, 2013 ITC Holdings Senior Notes, due July 15, 2013	Jul. 03, 2013 ITC Holdings 2012 Term Loan Credit Agreement	Sep. 30, 2013 ITC Midwest	Apr. 04, 2013 ITC Midwest First Mortgage Bonds, Series F Secured Debt	Sep. 30, 2013 ITC Great Plains	Sep. 30, 2013 ITC Great Plains Term Loan Credit Agreement Unsecured Debt	Sep. 30, 2013 ITCTransmission	Aug. 14, 2013 ITCTransmission Term Loan Credit Agreement	Sep. 30, 2013 ITCTransmission Term Loan Credit Agreement Unsecured Debt	Jul. 11, 2013 ITCTransmission Term Loan Credit Agreement Unsecured Debt	Jul. 11, 2013 ITCTransmission First Mortgage Bonds, due July 15, 2013	Aug. 14, 2013 ITCTransmission First Mortgage Bonds, Series E Secured Debt	Aug. 14, 2013 ITCTransmission Intercompany Credit Agreement
Debt Instrument
Short-term debt					$ 160,000,000	$ 250,000,000
Short-term debt, maximum borrowing capacity						250,000,000
Principal amount							250,000,000	300,000,000				100,000,000								285,000,000
Interest rate							4.05%	5.30%				4.09%								4.625%
Retirement of debt	452,000,000	0							267,000,000										185,000,000
Repayment of debt	475,000,000	0								200,000,000						185,000,000					100,000,000
Weighted average interest rate				[1]	1.20%						1.20%		1.90%	1.00%	1.30%
Other long-term debt														100,000,000			0	185,000,000
Other long-term debt, maximum borrowing capacity														$ 100,000,000				$ 185,000,000

[1] Loan bears interest at a rate equal to LIBOR plus an applicable margin of 1.75% or at a base rate, which is defined as the higher of the prime rate, 0.50% above the federal funds rate or 1% above the one month LIBOR, plus an applicable margin of 0.75%, subject to adjustments based on ITC Holdings’ credit rating.