v3.26.1
Pension and Other Postretirement Benefits (OPEB) - Additional Information (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Pension Plan [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Total benefit costs $ 8 $ 18
Pension Plan [Member] | Maximum [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Defined benefit plan, expected future employer contributions, current fiscal year 100  
Postretirement Healthcare Plans [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Total benefit costs (2) 1
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 15  
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Pension Plan [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Total benefit costs 4 6
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Postretirement Healthcare Plans [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Total benefit costs $ 3 $ 3