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Jointly Owned Utility Facilities - NPC (Details)
$ in Millions
Dec. 31, 2024
USD ($)
Jointly Owned Utility Plant Interests [Line Items]  
Facility in service $ 10,708
Accumulated depreciation 6,415
Construction work in progress 465
NPC  
Jointly Owned Utility Plant Interests [Line Items]  
Facility in service 180
Accumulated depreciation 60
Construction work in progress $ 2
NPC | ON Line Transmission Line  
Jointly Owned Utility Plant Interests [Line Items]  
Ownership share 19.00%
Facility in service $ 121
Accumulated depreciation 31
Construction work in progress 1
NPC | Other transmission facilities  
Jointly Owned Utility Plant Interests [Line Items]  
Facility in service 59
Accumulated depreciation 29
Construction work in progress $ 1