v3.26.1
Derivative Instruments (Significant Unobservable Inputs) (Details) - Level 3
 6 Months Ended
Jun. 30, 2026
USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Assets, Fair Value Disclosure $ 1,933,000,000
Financial and Nonfinancial Liabilities, Fair Value Disclosure 1,178,000,000
Forward Contracts - Power [Member] | Forward Contracts - Power [Member] | Forward Price [Member] | Maximum | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Forward price (in dollars per energy unit) 172
Forward Contracts - Power [Member] | Forward Contracts - Power [Member] | Forward Price [Member] | Minimum | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Forward price (in dollars per energy unit) 0
Forward Contracts - Power [Member] | Forward Contracts - Power [Member] | Forward Price [Member] | Weighted Average [Member] | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Forward price (in dollars per energy unit) 54
Forward Contracts - Power [Member] | Derivative Financial Instruments, Assets [Member] | Forward Contracts - Power [Member] | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Assets, Fair Value Disclosure 474,000,000
Forward contracts - Gas [Member] | Forward contracts - Gas [Member] | Forward Price [Member] | Maximum | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Forward price (in dollars per energy unit) 19
Forward contracts - Gas [Member] | Forward contracts - Gas [Member] | Forward Price [Member] | Minimum | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Forward price (in dollars per energy unit) 0
Forward contracts - Gas [Member] | Forward contracts - Gas [Member] | Forward Price [Member] | Weighted Average [Member] | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Forward price (in dollars per energy unit) 3
Forward contracts - Gas [Member] | Derivative Financial Instruments, Assets [Member] | Forward contracts - Gas [Member] | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Assets, Fair Value Disclosure 630,000,000
Forward contracts - Congestion [Member] | Forward contracts - Congestion [Member] | Forward Price [Member] | Maximum | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Forward price (in dollars per energy unit) 26
Forward contracts - Congestion [Member] | Forward contracts - Congestion [Member] | Forward Price [Member] | Minimum | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Forward price (in dollars per energy unit) (62)
Forward contracts - Congestion [Member] | Forward contracts - Congestion [Member] | Forward Price [Member] | Weighted Average [Member] | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Forward price (in dollars per energy unit) 0
Forward contracts - Congestion [Member] | Derivative Financial Instruments, Assets [Member] | Forward contracts - Congestion [Member] | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Assets, Fair Value Disclosure $ 69,000,000
Option Contracts, Power [Member] | Option Contracts, Power [Member] | Implied Correlations [Member] | Maximum | Option Models [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 73.00%
Option Contracts, Power [Member] | Option Contracts, Power [Member] | Implied Correlations [Member] | Minimum | Option Models [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 69.00%
Option Contracts, Power [Member] | Option Contracts, Power [Member] | Implied Correlations [Member] | Weighted Average [Member] | Option Models [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 71.00%
Option Contracts, Power [Member] | Option Contracts, Power [Member] | Implied Volatilities [Member] | Maximum | Option Models [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 325.00%
Option Contracts, Power [Member] | Option Contracts, Power [Member] | Implied Volatilities [Member] | Minimum | Option Models [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 35.00%
Option Contracts, Power [Member] | Option Contracts, Power [Member] | Implied Volatilities [Member] | Weighted Average [Member] | Option Models [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 92.00%
Option Contracts, Power [Member] | Derivative Financial Instruments, Assets [Member] | Option Contracts, Power [Member] | Option Models [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Assets, Fair Value Disclosure $ 24,000,000
Option Contracts, Primarily Gas [Member] | Option Contracts, Gas [Member] | Implied Correlations [Member] | Maximum | Option Models [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] | Option Contracts, Gas [Member] | Implied Correlations [Member] | Minimum | Option Models [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] | Option Contracts, Gas [Member] | Implied Correlations [Member] | Weighted Average [Member] | Option Models [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 97.00%
Option Contracts, Primarily Gas [Member] | Option Contracts, Gas [Member] | Implied Volatilities [Member] | Maximum | Option Models [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 82.00%
Option Contracts, Primarily Gas [Member] | Option Contracts, Gas [Member] | Implied Volatilities [Member] | Minimum | Option Models [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] | Option Contracts, Gas [Member] | Implied Volatilities [Member] | Weighted Average [Member] | Option Models [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 43.00%
Option Contracts, Primarily Gas [Member] | Derivative Financial Instruments, Assets [Member] | Option Contracts, Gas [Member] | Option Models [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Assets, Fair Value Disclosure $ 58,000,000
Full Requirements and Unit Contingent Contracts [Member] | Full Requirements and Unit Contingent Contracts [Member] | Forward Price [Member] | Maximum | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Forward price (in dollars per energy unit) 324
Full Requirements and Unit Contingent Contracts [Member] | Full Requirements and Unit Contingent Contracts [Member] | Forward Price [Member] | Minimum | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Forward price (in dollars per energy unit) 16
Full Requirements and Unit Contingent Contracts [Member] | Full Requirements and Unit Contingent Contracts [Member] | Forward Price [Member] | Weighted Average [Member] | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Forward price (in dollars per energy unit) $ 94
Full Requirements and Unit Contingent Contracts [Member] | Full Requirements and Unit Contingent Contracts [Member] | Customer Migration Rate [Member] | Maximum | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Fair Value Inputs, Expected Rates 12.00%
Full Requirements and Unit Contingent Contracts [Member] | Full Requirements and Unit Contingent Contracts [Member] | Customer Migration Rate [Member] | Minimum | Discounted Cash Flow 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] | Full Requirements and Unit Contingent Contracts [Member] | Customer Migration Rate [Member] | Weighted Average [Member] | Discounted Cash Flow 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] | Full Requirements and Unit Contingent Contracts [Member] | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Assets, Fair Value Disclosure $ 187,000,000
Forward contracts - Other [Member] [Member] | Derivative Financial Instruments, Assets [Member] | Forward contracts - Other [Member] [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Assets, Fair Value Disclosure 491,000,000
Derivative Financial Instruments, Liabilities [Member] | Forward Contracts - Power [Member] | Forward Contracts - Power [Member] | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Financial and Nonfinancial Liabilities, Fair Value Disclosure 328,000,000
Derivative Financial Instruments, Liabilities [Member] | Forward contracts - Gas [Member] | Forward contracts - Gas [Member] | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Financial and Nonfinancial Liabilities, Fair Value Disclosure 161,000,000
Derivative Financial Instruments, Liabilities [Member] | Forward contracts - Congestion [Member] | Forward contracts - Congestion [Member] | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Financial and Nonfinancial Liabilities, Fair Value Disclosure 53,000,000
Derivative Financial Instruments, Liabilities [Member] | Option Contracts, Power [Member] | Option Contracts, Power [Member] | Option Models [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Financial and Nonfinancial Liabilities, Fair Value Disclosure 0
Derivative Financial Instruments, Liabilities [Member] | Option Contracts, Primarily Gas [Member] | Option Contracts, Gas [Member] | Option Models [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Financial and Nonfinancial Liabilities, Fair Value Disclosure 66,000,000
Derivative Financial Instruments, Liabilities [Member] | Full Requirements and Unit Contingent Contracts [Member] | Full Requirements and Unit Contingent Contracts [Member] | Discounted Cash Flow Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Financial and Nonfinancial Liabilities, Fair Value Disclosure 316,000,000
Derivative Financial Instruments, Liabilities [Member] | Forward contracts - Other [Member] [Member] | Forward contracts - Other [Member] [Member]  
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Financial and Nonfinancial Liabilities, Fair Value Disclosure $ 254,000,000