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Jointly Owned Utility Facilities - SPPC (Details)
$ in Millions
Dec. 31, 2021
USD ($)
Jointly Owned Utility Plant Interests [Line Items]  
Facility in service $ 10,504
Accumulated depreciation 5,498
Construction work in progress 246
SPPC  
Jointly Owned Utility Plant Interests [Line Items]  
Facility in service 438
Accumulated depreciation 319
Construction work in progress $ 1
SPPC | Valmy  
Jointly Owned Utility Plant Interests [Line Items]  
Ownership share 50.00%
Facility in service $ 394
Accumulated depreciation 309
Construction work in progress $ 1
SPPC | ON Line deferrals  
Jointly Owned Utility Plant Interests [Line Items]  
Ownership share 6.00%
Facility in service $ 40
Accumulated depreciation 8
Construction work in progress $ 0
SPPC | Valmy Transmission  
Jointly Owned Utility Plant Interests [Line Items]  
Ownership share 50.00%
Facility in service $ 4
Accumulated depreciation 2
Construction work in progress $ 0