DEBT Schedule of Revolving Credit Agreements (Details) (USD $)	9 Months Ended
	Sep. 30, 2013
Line of Credit Facility
Total available capacity	$ 725,000,000
Outstanding balance	214,100,000
Unused capacity	510,900,000
ITC Holdings
Line of Credit Facility
Total available capacity	200,000,000.0
Outstanding balance	0	[1]
Unused capacity	200,000,000
Weighted average interest rate		[2]
Commitment fee rate	0.25%	[3]
Original term	5 years
Interest rate description	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.
ITCTransmission
Line of Credit Facility
Total available capacity	100,000,000.0
Outstanding balance	28,300,000	[1]
Unused capacity	71,700,000
Weighted average interest rate	1.30%
Commitment fee rate	0.125%	[3]
Original term	5 years
METC
Line of Credit Facility
Total available capacity	100,000,000.0
Outstanding balance	54,400,000	[1]
Unused capacity	45,600,000
Weighted average interest rate	1.30%
Commitment fee rate	0.125%	[3]
Original term	5 years
ITC Midwest
Line of Credit Facility
Total available capacity	175,000,000
Outstanding balance	94,700,000	[1]
Unused capacity	80,300,000
Weighted average interest rate	1.20%
Commitment fee rate	0.10%	[3]
Original term	5 years
ITC Great Plains
Line of Credit Facility
Total available capacity	150,000,000
Outstanding balance	36,700,000	[1]
Unused capacity	$ 113,300,000
Weighted average interest rate	1.90%
Commitment fee rate	0.30%	[3]
Original term	4 years

[1] Included within long-term debt.

[2] 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.

[3] Calculation based on the average daily unused commitments, subject to adjustment based on the borrower’s credit rating.