v3.26.3
COMMITMENTS, GUARANTEES AND CONTINGENCIES - Narrative (Details)
 3 Months Ended 9 Months Ended
Sep. 30, 2026
USD ($)
unit
a
uncommittedFacility
Jun. 30, 2024
USD ($)
Sep. 30, 2026
USD ($)
unit
a
uncommittedFacility
Jun. 30, 2026
USD ($)
Apr. 30, 2026
USD ($)
Mar. 31, 2026
USD ($)
Jan. 31, 2026
USD ($)
Other Commitments [Line Items]              
Number of uncommitted facilities | uncommittedFacility 7   7        
Liabilities incurred     $ 11,000,000        
Area of land closed, noncompliant with CCR rule | a 300   300        
CCR Rule Revision              
Other Commitments [Line Items]              
Liabilities incurred   $ 674,000,000          
Revolving Credit Facility | Letter of Credit              
Other Commitments [Line Items]              
Letters of credit outstanding, amount $ 0   $ 0        
Revolving Credit Facility | Letter of Credit | Subsidiaries              
Other Commitments [Line Items]              
Line of credit facility, borrowing capacity 1,200,000,000   1,200,000,000        
Revolving Credit Facility | Revolving Credit Facility, Due April 2031 | Line of Credit              
Other Commitments [Line Items]              
Line of credit facility, borrowing capacity         $ 6,500,000,000 $ 5,000,000,000  
Revolving Credit Facility | Revolving Credit Facility, Due March 2027 | Line of Credit              
Other Commitments [Line Items]              
Line of credit facility, borrowing capacity           $ 1,000,000,000  
Revolving Credit Facility | Revolving Credit Facility, Due April 2029 | Line of Credit              
Other Commitments [Line Items]              
Line of credit facility, borrowing capacity         $ 1,500,000,000    
Letter of Credit | Line of Credit              
Other Commitments [Line Items]              
Debt instrument, face amount 850,000,000   850,000,000        
Long-term line of credit       $ 131,000,000      
INDIANA MICHIGAN POWER COMPANY              
Other Commitments [Line Items]              
Unrecorded unconditional purchase obligation, to be paid 782,000,000   782,000,000        
Unrecorded unconditional purchase obligation, to be paid, remainder of fiscal year 31,000,000   31,000,000        
Unrecorded unconditional purchase obligation, to be paid, year one 497,000,000   497,000,000        
Unrecorded unconditional purchase obligation, to be paid, year two 145,000,000   145,000,000        
Recorded unconditional purchase obligation, to be paid, year four $ 31,000,000   $ 31,000,000        
INDIANA MICHIGAN POWER COMPANY | Cook Plant              
Other Commitments [Line Items]              
Nuclear contingencies, number of units | unit 2   2        
PUBLIC SERVICE COMPANY OF OKLAHOMA              
Other Commitments [Line Items]              
Unrecorded unconditional purchase obligation, to be paid $ 349,000,000   $ 349,000,000        
Unrecorded unconditional purchase obligation, to be paid, remainder of fiscal year 54,000,000   54,000,000        
Unrecorded unconditional purchase obligation, to be paid, year one 129,000,000   129,000,000        
Recorded unconditional purchase obligation, to be paid, year two and three 9,000,000   9,000,000        
Liabilities incurred     8,000,000        
APPALACHIAN POWER COMPANY | CCR Rule Revision              
Other Commitments [Line Items]              
Asset retirement obligation, approved recovery amount             $ 80,000,000
SOUTHWESTERN ELECTRIC POWER COMPANY              
Other Commitments [Line Items]              
Liabilities incurred     0        
Probable credit $ 22,000,000   $ 45,000,000        
Ohio Valley Electric Corporation | OHIO POWER COMPANY              
Other Commitments [Line Items]              
Ownership interest transferred to parent       4.30%      
Power participation entitlement interest transferred to parent       19.93%