v3.26.1
Fair Value of Financial Instruments - Derivative Fair Value Measurements (Details)
$ in Millions
Jun. 30, 2026
USD ($)
certificate
$ / MWh
$ / MMBTU
$ / MWd
Dec. 31, 2025
USD ($)
$ / MWh
certificate
$ / MMBTU
$ / MWd
Liabilities    
Derivative liabilities   $ 3,222
Commodity contracts    
Assets    
Derivative assets $ 4,783 3,754
Liabilities    
Derivative liabilities 4,176 3,070
Interest rate contracts    
Assets    
Derivative assets 10  
Liabilities    
Derivative liabilities   4
Level 3    
Assets    
Derivative assets 260 313
Liabilities    
Derivative liabilities 525 486
Level 3 | Renewable Energy Certificates    
Assets    
Derivative assets 18 12
Liabilities    
Derivative liabilities $ 35 $ 25
Level 3 | Renewable Energy Certificates | Low | Valuation Technique, Discounted Cash Flow | Forward Market Price (perMMBtu) or (per MWh)    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input | certificate 2 2
Level 3 | Renewable Energy Certificates | High | Valuation Technique, Discounted Cash Flow | Forward Market Price (perMMBtu) or (per MWh)    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input | certificate 370 370
Level 3 | Renewable Energy Certificates | Weighted Average | Valuation Technique, Discounted Cash Flow | Forward Market Price (perMMBtu) or (per MWh)    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input | certificate 18 17
Level 3 | Power Options | Low | Valuation Technique Option Model | Volatilities    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input   0.22
Level 3 | Power Options | High | Valuation Technique Option Model | Volatilities    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input   5.17
Level 3 | Power Options | Weighted Average | Valuation Technique Option Model | Volatilities    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input   1.10
Level 3 | Commodity contracts | Natural Gas Contracts    
Assets    
Derivative assets $ 25 $ 47
Liabilities    
Derivative liabilities $ 16 $ 40
Level 3 | Commodity contracts | Natural Gas Contracts | Low | Valuation Technique, Discounted Cash Flow | Forward Market Price (perMMBtu) or (per MWh)    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input | $ / MMBTU 1 0
Level 3 | Commodity contracts | Natural Gas Contracts | High | Valuation Technique, Discounted Cash Flow | Forward Market Price (perMMBtu) or (per MWh)    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input | $ / MMBTU 18 17
Level 3 | Commodity contracts | Natural Gas Contracts | Weighted Average | Valuation Technique, Discounted Cash Flow | Forward Market Price (perMMBtu) or (per MWh)    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input | $ / MMBTU 5 5
Level 3 | Commodity contracts | Power Contracts    
Assets    
Derivative assets $ 131 $ 168
Liabilities    
Derivative liabilities $ 125 $ 64
Level 3 | Commodity contracts | Power Contracts | Low | Valuation Technique, Discounted Cash Flow | Forward Market Price (perMMBtu) or (per MWh)    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input | $ / MWh 0 0
Level 3 | Commodity contracts | Power Contracts | High | Valuation Technique, Discounted Cash Flow | Forward Market Price (perMMBtu) or (per MWh)    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input | $ / MWh 192 125
Level 3 | Commodity contracts | Power Contracts | Weighted Average | Valuation Technique, Discounted Cash Flow | Forward Market Price (perMMBtu) or (per MWh)    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input | $ / MWh 28 29
Level 3 | Commodity contracts | FTRs    
Assets    
Derivative assets $ 44 $ 22
Liabilities    
Derivative liabilities $ 25 $ 11
Level 3 | Commodity contracts | FTRs | Low | Valuation Technique, Discounted Cash Flow | Auction Prices ($ per MWh)    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input (74) (50)
Level 3 | Commodity contracts | FTRs | High | Valuation Technique, Discounted Cash Flow | Auction Prices ($ per MWh)    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input 25,013 19,100
Level 3 | Commodity contracts | FTRs | Weighted Average | Valuation Technique, Discounted Cash Flow | Auction Prices ($ per MWh)    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input 1 0
Level 3 | Capacity Contracts | Capacity Contracts    
Assets    
Derivative assets $ 22 $ 20
Liabilities    
Derivative liabilities $ 19 $ 18
Level 3 | Capacity Contracts | Capacity Contracts | Low | Valuation Technique, Discounted Cash Flow | Forward Market Price (perMMBtu) or (per MWh)    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input | $ / MWd 54 49
Level 3 | Capacity Contracts | Capacity Contracts | High | Valuation Technique, Discounted Cash Flow | Forward Market Price (perMMBtu) or (per MWh)    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input | $ / MWd 625 577
Level 3 | Capacity Contracts | Capacity Contracts | Weighted Average | Valuation Technique, Discounted Cash Flow | Forward Market Price (perMMBtu) or (per MWh)    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input | $ / MWd 331 270
Level 3 | Power Options | Power Options    
Assets    
Derivative assets $ 20 $ 44
Liabilities    
Derivative liabilities $ 34 45
Level 3 | Power Options | Power Options | Low | Valuation Technique Option Model | Volatilities    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input 0.32  
Level 3 | Power Options | Power Options | High | Valuation Technique Option Model | Volatilities    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input 6.94  
Level 3 | Power Options | Power Options | Weighted Average | Valuation Technique Option Model | Volatilities    
Fair Value Inputs / Range    
Derivative asset/liability, measurement input 1.31  
Level 3 | Interest rate contracts    
Assets    
Derivative assets $ 0  
Liabilities    
Derivative liabilities   $ 0
Level 3 | Interest rate contracts | Low | Valuation Technique, Discounted Cash Flow | Collateral Prepayment Rates    
Fair Value Inputs / Range    
Derivative liability, measurement input 0.0200 0.0200
Level 3 | Interest rate contracts | Low | Valuation Technique, Discounted Cash Flow | Credit Loss Rates    
Fair Value Inputs / Range    
Derivative liability, measurement input 0.0653 0.0640
Level 3 | Interest rate contracts | High | Valuation Technique, Discounted Cash Flow | Collateral Prepayment Rates    
Fair Value Inputs / Range    
Derivative liability, measurement input 0.0300 0.0300
Level 3 | Interest rate contracts | High | Valuation Technique, Discounted Cash Flow | Credit Loss Rates    
Fair Value Inputs / Range    
Derivative liability, measurement input 0.6000 0.6000
Level 3 | Interest rate contracts | Weighted Average | Valuation Technique, Discounted Cash Flow | Collateral Prepayment Rates    
Fair Value Inputs / Range    
Derivative liability, measurement input 0.0248 0.0252
Level 3 | Interest rate contracts | Weighted Average | Valuation Technique, Discounted Cash Flow | Credit Loss Rates    
Fair Value Inputs / Range    
Derivative liability, measurement input 0.1770 0.1694
Level 3 | Interest rate contracts | Consumer Financing Program    
Assets    
Derivative assets $ 0 $ 0
Liabilities    
Derivative liabilities $ 271 $ 283
Level 3 | Interest rate contracts | Consumer Financing Program | Low | Valuation Technique, Discounted Cash Flow | Collateral Default Rates    
Fair Value Inputs / Range    
Derivative liability, measurement input 0.0074 0.0118
Level 3 | Interest rate contracts | Consumer Financing Program | High | Valuation Technique, Discounted Cash Flow | Collateral Default Rates    
Fair Value Inputs / Range    
Derivative liability, measurement input 0.4350 0.4200
Level 3 | Interest rate contracts | Consumer Financing Program | Weighted Average | Valuation Technique, Discounted Cash Flow | Collateral Default Rates    
Fair Value Inputs / Range    
Derivative liability, measurement input 0.0858 0.0786