v3.26.1
Fair Value of Financial Instruments - Schedule of Fair Value Measurement Inputs and Valuation Techniques (Details) - Level 3
$ in Millions
Jun. 30, 2026
USD ($)
MWh
$ / BTU
$ / MWh
Low | Forward Market Price | Option Model  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Input/Range | $ / BTU 2.15
High | Forward Market Price | Option Model  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Input/Range | $ / BTU 9.91
Weighted Average | Forward Market Price | Option Model  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Input/Range | $ / BTU 2.66
Long-term Power Commodity Contracts | Discounted Cash Flow  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Assets | $ $ 0
Liabilities | $ $ 80
Long-term Power Commodity Contracts | Low | Forward Market Price | Discounted Cash Flow  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Input/Range | $ / MWh 31.47
Long-term Power Commodity Contracts | High | Forward Market Price | Discounted Cash Flow  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Input/Range | $ / MWh 79.85
Long-term Power Commodity Contracts | Weighted Average | Forward Market Price | Discounted Cash Flow  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Input/Range | $ / MWh 48.47
Heat Rate Call Option Commodity Contracts | Option Model  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Assets | $ $ 20
Liabilities | $ $ 2
Heat Rate Call Option Commodity Contracts | Low | Forward Market Price | Option Model  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Input/Range | $ / MWh 2.26
Heat Rate Call Option Commodity Contracts | High | Forward Market Price | Option Model  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Input/Range | $ / MWh 256.49
Heat Rate Call Option Commodity Contracts | Weighted Average | Forward Market Price | Option Model  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Input/Range | $ / MWh 44.08
Other Financial Instruments | Discounted Cash Flow  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Assets | $ $ 4
Liabilities | $ $ 0
Other Financial Instruments | Low | Forward Market Price | Discounted Cash Flow  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Input/Range | MWh 57,935
Other Financial Instruments | High | Forward Market Price | Discounted Cash Flow  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Input/Range | MWh 115,869
Other Financial Instruments | Weighted Average | Forward Market Price | Discounted Cash Flow  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Input/Range | MWh 97,214