v3.26.3
Derivative Instruments (Significant Unobservable Inputs) (Details) - Level 3
 9 Months Ended
Sep. 30, 2026
USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Assets, Fair Value Disclosure $ 1,818,000,000
Financial and Nonfinancial Liabilities, Fair Value Disclosure 1,140,000,000
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) 1
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) 55
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 615,000,000
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) 10
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) 1
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 568,000,000
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) 30
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) (66)
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 $ 76,000,000
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 74.00%
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 59.00%
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 244.00%
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 32.00%
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 96.00%
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 $ 39,000,000
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 59.00%
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 93.00%
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 17.00%
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 48.00%
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 $ 59,000,000
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) 378
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) $ 93
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 10.00%
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 $ 167,000,000
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 294,000,000
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 327,000,000
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 75,000,000
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 2,000,000
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 64,000,000
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 326,000,000
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 $ 293,000,000