v3.25.4
Derivative Instruments and Hedging Activities (Significant Unobservable Inputs) (Details)
 12 Months Ended
Dec. 31, 2025
USD ($)
BTU
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Number Of British Thermal Units | BTU 1,000,000
Level 3  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Assets, Fair Value Disclosure $ 1,850,000,000
Liabilities, Fair Value Disclosure 1,168,000,000
Forward Contracts - Power [Member] | Level 3 | Forward Contracts - Power [Member] | Forward Price [Member] | Maximum [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Offered Quotes, Price Per Energy Unit 333
Forward Contracts - Power [Member] | Level 3 | Forward Contracts - Power [Member] | Forward Price [Member] | Minimum [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Offered Quotes, Price Per Energy Unit 0
Forward Contracts - Power [Member] | Level 3 | Forward Contracts - Power [Member] | Forward Price [Member] | Weighted Average [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Offered Quotes, Price Per Energy Unit 53
Forward Contracts - Power [Member] | Derivative Financial Instruments, Assets [Member] | Level 3 | Forward Contracts - Power [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Assets, Fair Value Disclosure 486,000,000
Forward contracts - Gas [Member] | Level 3 | Forward contracts - Gas [Member] | Forward Price [Member] | Maximum [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Offered Quotes, Price Per Energy Unit 15
Forward contracts - Gas [Member] | Level 3 | Forward contracts - Gas [Member] | Forward Price [Member] | Minimum [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Offered Quotes, Price Per Energy Unit 0
Forward contracts - Gas [Member] | Level 3 | Forward contracts - Gas [Member] | Forward Price [Member] | Weighted Average [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Offered Quotes, Price Per Energy Unit 4
Forward contracts - Gas [Member] | Derivative Financial Instruments, Assets [Member] | Level 3 | Forward contracts - Gas [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Assets, Fair Value Disclosure $ 455,000,000
Option Contracts, Power [Member] | Level 3 | Option Contracts, Power [Member] | Implied Correlations [Member] | Maximum [Member] | Options Models, Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 75.00%
Option Contracts, Power [Member] | Level 3 | Option Contracts, Power [Member] | Implied Correlations [Member] | Minimum [Member] | Options Models, Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 69.00%
Option Contracts, Power [Member] | Level 3 | Option Contracts, Power [Member] | Implied Correlations [Member] | Weighted Average [Member] | Options Models, Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 71.00%
Option Contracts, Power [Member] | Level 3 | Option Contracts, Power [Member] | Implied Volatilities [Member] | Maximum [Member] | Options Models, Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 312.00%
Option Contracts, Power [Member] | Level 3 | Option Contracts, Power [Member] | Implied Volatilities [Member] | Minimum [Member] | Options Models, Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 37.00%
Option Contracts, Power [Member] | Level 3 | Option Contracts, Power [Member] | Implied Volatilities [Member] | Weighted Average [Member] | Options Models, Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 91.00%
Option Contracts, Power [Member] | Derivative Financial Instruments, Assets [Member] | Level 3 | Option Contracts, Power [Member] | Options Models, Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Assets, Fair Value Disclosure $ 23,000,000
Option Contracts, Primarily Gas [Member] | Level 3 | Options - primarily gas [Member] | Implied Correlations [Member] | Maximum [Member] | Options Models, Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 100.00%
Option Contracts, Primarily Gas [Member] | Level 3 | Options - primarily gas [Member] | Implied Correlations [Member] | Minimum [Member] | Options Models, Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 69.00%
Option Contracts, Primarily Gas [Member] | Level 3 | Options - primarily gas [Member] | Implied Correlations [Member] | Weighted Average [Member] | Options Models, Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 94.00%
Option Contracts, Primarily Gas [Member] | Level 3 | Options - primarily gas [Member] | Implied Volatilities [Member] | Maximum [Member] | Options Models, Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 145.00%
Option Contracts, Primarily Gas [Member] | Level 3 | Options - primarily gas [Member] | Implied Volatilities [Member] | Minimum [Member] | Options Models, Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 16.00%
Option Contracts, Primarily Gas [Member] | Level 3 | Options - primarily gas [Member] | Implied Volatilities [Member] | Weighted Average [Member] | Options Models, Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 46.00%
Option Contracts, Primarily Gas [Member] | Derivative Financial Instruments, Assets [Member] | Level 3 | Options - primarily gas [Member] | Options Models, Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Assets, Fair Value Disclosure $ 71,000,000
Full Requirements and Unit Contingent Contracts [Member] | Level 3 | Full Requirements and Unit Contingent Contracts [Member] | Forward Price [Member] | Maximum [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Offered Quotes, Price Per Energy Unit 430
Full Requirements and Unit Contingent Contracts [Member] | Level 3 | Full Requirements and Unit Contingent Contracts [Member] | Forward Price [Member] | Minimum [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Offered Quotes, Price Per Energy Unit 19
Full Requirements and Unit Contingent Contracts [Member] | Level 3 | Full Requirements and Unit Contingent Contracts [Member] | Forward Price [Member] | Weighted Average [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Offered Quotes, Price Per Energy Unit $ 90
Full Requirements and Unit Contingent Contracts [Member] | Level 3 | Full Requirements and Unit Contingent Contracts [Member] | Customer Migration Rate [Member] | Maximum [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 28.00%
Full Requirements and Unit Contingent Contracts [Member] | Level 3 | Full Requirements and Unit Contingent Contracts [Member] | Customer Migration Rate [Member] | Minimum [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 0.00%
Full Requirements and Unit Contingent Contracts [Member] | Level 3 | Full Requirements and Unit Contingent Contracts [Member] | Customer Migration Rate [Member] | Weighted Average [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 1.00%
Full Requirements and Unit Contingent Contracts [Member] | Derivative Financial Instruments, Assets [Member] | Level 3 | Full Requirements and Unit Contingent Contracts [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Assets, Fair Value Disclosure $ 193,000,000
Forward contracts - Other | Derivative Financial Instruments, Assets [Member] | Level 3 | Forward contracts - Other  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Assets, Fair Value Disclosure 575,000,000
Forward contracts - Other | Derivative Financial Instruments, Assets [Member] | Level 3 | Forward contracts - Congestion | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Assets, Fair Value Disclosure 47,000,000
Forward contracts - Congestion | Level 3 | Forward contracts - Congestion | Forward Price [Member] | Maximum [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Offered Quotes, Price Per Energy Unit 58
Forward contracts - Congestion | Level 3 | Forward contracts - Congestion | Forward Price [Member] | Minimum [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Offered Quotes, Price Per Energy Unit (63)
Forward contracts - Congestion | Level 3 | Forward contracts - Congestion | Forward Price [Member] | Weighted Average [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Offered Quotes, Price Per Energy Unit 0
Derivative Financial Instruments, Liabilities [Member] | Forward Contracts - Power [Member] | Level 3 | Forward Contracts - Power [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Liabilities, Fair Value Disclosure 378,000,000
Derivative Financial Instruments, Liabilities [Member] | Forward contracts - Gas [Member] | Level 3 | Forward contracts - Gas [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Liabilities, Fair Value Disclosure 129,000,000
Derivative Financial Instruments, Liabilities [Member] | Option Contracts, Power [Member] | Level 3 | Option Contracts, Power [Member] | Options Models, Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Liabilities, Fair Value Disclosure 1,000,000
Derivative Financial Instruments, Liabilities [Member] | Option Contracts, Primarily Gas [Member] | Level 3 | Options - primarily gas [Member] | Options Models, Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Liabilities, Fair Value Disclosure 82,000,000
Derivative Financial Instruments, Liabilities [Member] | Full Requirements and Unit Contingent Contracts [Member] | Level 3 | Full Requirements and Unit Contingent Contracts [Member] | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Liabilities, Fair Value Disclosure 296,000,000
Derivative Financial Instruments, Liabilities [Member] | Forward contracts - Other | Level 3 | Forward contracts - Other  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Liabilities, Fair Value Disclosure 259,000,000
Derivative Financial Instruments, Liabilities [Member] | Forward contracts - Other | Level 3 | Forward contracts - Congestion | Discounted Cash Flow Valuation Technique [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Liabilities, Fair Value Disclosure $ 23,000,000