v3.26.1
DEBT (Details) - USD ($)
$ in Millions
Jul. 15, 2026
Jun. 30, 2026
Apr. 01, 2026
Mar. 12, 2026
Jan. 14, 2026
Debt Instrument [Line Items]          
Debt Instrument, Face Amount   $ 1,500      
ITC Holdings Corp.          
Debt Instrument [Line Items]          
Commercial Paper Program, Maximum Authorized Amount Outstanding   400      
Commercial Paper   $ 0      
ITC Holdings Corp. | Unsecured Debt          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount     $ 900    
ITC Holdings Corp. | Senior Notes, due April 15, 2031 | Unsecured Debt          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount     $ 500    
Debt Instrument, Interest Rate, Stated Percentage     4.875%    
ITC Holdings Corp. | Senior Notes, due April 15, 2036 | Unsecured Debt          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount     $ 400    
Debt Instrument, Interest Rate, Stated Percentage     5.50%    
ITC Midwest LLC | First Mortgage Bonds, Series O, due March 12, 2035 | Secured Debt          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount       $ 175  
Debt Instrument, Interest Rate, Stated Percentage       4.86%  
ITC Midwest LLC | First Mortgage Bonds, Series P, due July 15, 2047 | Secured Debt | Subsequent Event          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 100        
Debt Instrument, Interest Rate, Stated Percentage 5.53%        
ITCTransmission | First Mortgage Bonds, Series M, due March 12, 2034 | Secured Debt          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount       $ 175  
Debt Instrument, Interest Rate, Stated Percentage       4.78%  
ITCTransmission | First Mortgage Bonds, Series N, due July 15, 2044 | Secured Debt | Subsequent Event          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount $ 50        
Debt Instrument, Interest Rate, Stated Percentage 5.41%        
METC LLC | Senior Secured Notes, Series A, due January 14, 2036 | Secured Debt          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount         $ 125
Debt Instrument, Interest Rate, Stated Percentage         5.08%
METC LLC | Senior Secured Notes, Series B, due January 14, 2046 | Secured Debt          
Debt Instrument [Line Items]          
Debt Instrument, Face Amount         $ 125
Debt Instrument, Interest Rate, Stated Percentage         5.71%