DEBT Interest Rate Swap Agreements (Details) - USD ($)			1 Months Ended
		Dec. 31, 2014	Feb. 25, 2016	Jan. 31, 2015	Oct. 31, 2014	Aug. 31, 2014	Dec. 31, 2015
Interest Rate Swaps
Long-term debt		$ 3,629,800,000					$ 3,680,400,000
Interest Rate Swap
Interest Rate Swaps
Notional amount				$ 25,000,000	$ 25,000,000	$ 25,000,000	75,000,000
Derivative, fixed interest rate				2.301%	3.075%	3.217%
Term of contract				10 years	10 years	10 years
Ineffectiveness recorded in the consolidated statement of operations		0
Interest Rate Swap | Fair Value, Inputs, Level 2 | Recurring Basis
Interest Rate Swaps
Derivative asset							112,000
Derivative liability		1,934,000					3,548,000
ITC Holdings Corp.
Interest Rate Swaps
Long-term debt		1,920,700,000					1,921,300,000
Senior Notes, due September 30, 2016 | Unsecured Debt | ITC Holdings Corp.
Interest Rate Swaps
Long-term debt	[1]	$ 139,338,000					$ 139,341,000	[2]
Subsequent Event | Interest Rate Swap | Tranche One
Interest Rate Swaps
Notional amount			$ 25,000,000
Derivative, fixed interest rate			1.77%
Term of contract			10 years
Subsequent Event | Interest Rate Swap | Tranche Two
Interest Rate Swaps
Notional amount			$ 25,000,000
Derivative, fixed interest rate			1.619%
Term of contract			10 years

[1] The debt obligations were partially retired prior to maturity date through the cash tender offer described below.

[2] As of December 31, 2015 and 2014, there was $395.3 million and $175.0 million, respectively, of debt included within debt maturing within one year that is classified as a current liability in the consolidated statements of financial position.