v3.26.1
ORGANIZATION AND BASIS OF PRESENTATION (Details)
$ in Millions
3 Months Ended
Feb. 13, 2026
Feb. 26, 2025
USD ($)
transmission_project
Mar. 31, 2026
USD ($)
segment
mi
kV
Mar. 31, 2025
USD ($)
Dec. 31, 2025
USD ($)
Feb. 21, 2025
Mar. 25, 2024
director
May 31, 2022
Regulatory Asset [Line Items]                
Service area | mi     12,515          
Nominal voltage (in kV)     500          
Nominal voltage (in kV)     345          
Nominal voltage (in kV)     230          
Nominal voltage (in kV)     138          
Nominal voltage (in kV)     115          
Nominal voltage (in kV)     69          
Nominal voltage (in kV)     46          
Number of directors | director             5  
Capitalized cost of equity | $     $ 17 $ 12        
Capitalized interest | $     $ 6 $ 4        
Number of operating segments | segment     1          
Valley Link                
Regulatory Asset [Line Items]                
Equity method investment, ownership percentage           34.00%    
Valley Link | PJM Interconnection, LLC | PJM 2024 RTEP Window 1                
Regulatory Asset [Line Items]                
Number of transmission projects | transmission_project   2            
Transmission solutions to the reliability issues | $   $ 3,000            
Valley Link | Dominion HV                
Regulatory Asset [Line Items]                
Equity method investment, ownership percentage           30.00%    
Valley Link | Transource Energy, LLC                
Regulatory Asset [Line Items]                
Equity method investment, ownership percentage           36.00%    
Valley Link | FET | PJM Interconnection, LLC | PJM 2024 RTEP Window 1                
Regulatory Asset [Line Items]                
Transmission solutions to the reliability issues | $   $ 1,000            
FET | Brookfield                
Regulatory Asset [Line Items]                
Sale of ownership interest by parent             30.00%  
Path WV | Variable Interest Entity, Not Primary Beneficiary                
Regulatory Asset [Line Items]                
Equity method investments | $     $ 17   $ 17      
Variable interest entities percentage of high voltage transmission line project owned by variable interest entity one in joint venture party two     50.00%          
North American Transmission Company II LLC | FET | Brookfield                
Regulatory Asset [Line Items]                
Equity method investment, ownership percentage             49.90% 19.90%
Brookfield                
Regulatory Asset [Line Items]                
Number of directors | director             2  
Equity contribution from FE                
Regulatory Asset [Line Items]                
Number of directors | director             3  
Common Class B | MAIT                
Regulatory Asset [Line Items]                
Special purpose membership interest held, percentage of distributions     1          
Grid Growth | Transource                
Regulatory Asset [Line Items]                
Ownership interest 50.00%              
Grid Growth | FET                
Regulatory Asset [Line Items]                
Ownership interest 50.00%              
Grid Growth EHV Holdings, LLC | Grid Growth                
Regulatory Asset [Line Items]                
Ownership interest 80.00%              
MAIT | Common Class A                
Regulatory Asset [Line Items]                
Ownership percentage by parent             100.00%  
MAIT | Common Class B                
Regulatory Asset [Line Items]                
Ownership percentage by parent             100.00%  
FET | Equity contribution from FE                
Regulatory Asset [Line Items]                
Ownership percentage by parent             50.10%