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Pension and Other Postretirement Benefits (OPEB) - Additional Information (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Pension Plan [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Total benefit costs $ 18 $ 18 $ 55 $ 52
Defined benefit plan, expected future employer contributions, next fiscal year 100   100  
Postretirement Healthcare Plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Total benefit costs 1 1 2 4
Defined benefit plan, expected future employer contributions, current fiscal year 5   5  
Long Island Electric Utility Servco LLC Pension and OPEB [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Defined benefit plan, expected future employer contributions, current fiscal year 23   23  
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Pension Plan [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Total benefit costs 11 12 23 25
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Postretirement Healthcare Plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Total benefit costs $ 4 $ 3 $ 11 $ 10