DEBT (Details) - USD ($) $ in Millions		12 Months Ended
DEBT (Details) - USD ($) $ in Millions	Jun. 24, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Feb. 13, 2025	Dec. 10, 2024	May 09, 2024	Feb. 01, 2024	Jan. 23, 2024	Nov. 01, 2023	Jun. 01, 2023	Nov. 26, 2014
Debt Instrument
Commercial Paper		$ 0	$ 0
Repayments of Long-term Debt		525	$ 250	$ 500
Incremental interest rate swap \| Cash Flow Hedging \| Subsequent Event
Debt Instrument
Derivative, Notional Amount					$ 95
Total Interest Rate Swaps \| Cash Flow Hedging \| Subsequent Event
Debt Instrument
Derivative, Notional Amount					$ 230
Derivative, Average Fixed Interest Rate					3.56%
ITC Holdings Corp.
Debt Instrument
Commercial Paper Program, Maximum Authorized Amount Outstanding		$ 400
ITC Holdings Corp. \| Unsecured Debt
Debt Instrument
Principal amount											$ 800
ITC Holdings Corp. \| Senior Notes, due May 9, 2034 \| Unsecured Debt
Debt Instrument
Principal amount							$ 400
Interest rate		5.65%					5.65%
ITC Holdings Corp. \| Senior Note, due June 15, 2024 \| Unsecured Debt
Debt Instrument
Principal amount		$ 400
Interest rate		3.65%
ITC Holdings Corp. \| Senior Notes, Due June 1, 2033 \| Unsecured Debt
Debt Instrument
Principal amount											$ 500
Interest rate		5.40%	5.40%								5.40%
ITC Holdings Corp. \| Senior Notes Additional Principal, Due September 22, 2027 \| Unsecured Debt
Debt Instrument
Principal amount											$ 300
Interest rate											4.95%
ITC Holdings Corp. \| Senior Notes, Due September 22, 2027 \| Unsecured Debt
Debt Instrument
Principal amount											$ 900
Interest rate		4.95%	4.95%								4.95%
ITC Holdings Corp. \| Senior Notes, due July 1, 2023 \| Unsecured Debt
Debt Instrument
Principal amount		$ 250
Interest rate		4.05%
ITCTransmission \| First Mortgage Bonds, Series K due January 23, 2029 \| Secured Debt
Debt Instrument
Principal amount									$ 75
Interest rate		5.11%							5.11%
ITCTransmission \| First Mortgage Bonds, Series L due January 23, 2034 \| Secured Debt
Debt Instrument
Principal amount									$ 75
Interest rate		5.38%							5.38%
METC \| Secured Debt
Debt Instrument
Principal amount										$ 175
METC \| Senior Secured Notes, Series A, due November 1, 2028 \| Secured Debt
Debt Instrument
Principal amount										$ 90
Interest rate		5.65%								5.65%
METC \| Senior Secured Notes, due January 2034 \| Secured Debt
Debt Instrument
Principal amount								$ 85
Interest rate								5.98%
ITC Midwest \| First Mortgage Bonds, Series M, due December 10, 2035 \| Secured Debt
Debt Instrument
Principal amount						$ 125
Interest rate		4.88%				4.88%
ITC Midwest \| First Mortgage Bonds, Series N, due December 10, 2043 \| Secured Debt
Debt Instrument
Principal amount						$ 125
Interest rate		5.25%				5.25%
ITC Great Plains \| First Mortgage Bonds, Series A, due November 26, 2044 \| Secured Debt
Debt Instrument
Principal amount												$ 150
Interest rate		4.16%	4.16%									4.16%
Repayments of Long-term Debt	$ 50

ITC Holdings Corp. 10-K