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Regulatory Matters - NPC - Regulatory Assets (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Regulatory Assets [Line Items]    
Total regulatory assets $ 5,349 $ 5,565
Regulatory assets, current 1,136 1,398
Regulatory assets, noncurrent $ 4,213 4,167
Asset retirement obligations    
Regulatory Assets [Line Items]    
Regulatory asset, amortization period 19 years  
Total regulatory assets $ 1,031 930
Unrealized losses on regulated derivative contracts    
Regulatory Assets [Line Items]    
Regulatory asset, amortization period 1 year  
Total regulatory assets $ 182 173
NPC    
Regulatory Assets [Line Items]    
Total regulatory assets 583 1,085
Regulatory assets, current 124 586
Regulatory assets, noncurrent $ 459 499
NPC | Deferred energy costs    
Regulatory Assets [Line Items]    
Regulatory asset, amortization period 1 year  
Total regulatory assets $ 110 575
NPC | Merger costs from 1999 merger    
Regulatory Assets [Line Items]    
Regulatory asset, amortization period 20 years  
Total regulatory assets $ 95 100
NPC | Asset retirement obligations    
Regulatory Assets [Line Items]    
Regulatory asset, amortization period 7 years  
Total regulatory assets $ 66 69
NPC | Unrealized losses on regulated derivative contracts    
Regulatory Assets [Line Items]    
Regulatory asset, amortization period 1 year  
Total regulatory assets $ 57 68
NPC | Decommissioning costs    
Regulatory Assets [Line Items]    
Regulatory asset, amortization period 3 years  
Total regulatory assets $ 57 56
NPC | Deferred operating costs    
Regulatory Assets [Line Items]    
Regulatory asset, amortization period 18 years  
Total regulatory assets $ 39 41
NPC | ON Line deferrals    
Regulatory Assets [Line Items]    
Regulatory asset, amortization period 28 years  
Total regulatory assets $ 38 40
NPC | Legacy meters    
Regulatory Assets [Line Items]    
Regulatory asset, amortization period 8 years  
Total regulatory assets $ 30 34
NPC | Other    
Regulatory Assets [Line Items]    
Total regulatory assets $ 91 $ 102