Derivative Instruments and Hedging Activities (Significant Unobservable Inputs) (Details) - Level 3	12 Months Ended
	Dec. 31, 2023 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets, Fair Value Disclosure	$ 1,925,000,000
Liabilities, Fair Value Disclosure	974,000,000
Forward Contracts - Power [Member] | 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	210
Forward Contracts - Power [Member] | 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	(3)
Forward Contracts - Power [Member] | 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	49
Forward Contracts - Power [Member] | Derivative Financial Instruments, Assets [Member] | 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	500,000,000
Forward contracts - Gas [Member] | 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	13
Forward contracts - Gas [Member] | 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	1
Forward contracts - Gas [Member] | 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	3
Forward contracts - Gas [Member] | Derivative Financial Instruments, Assets [Member] | 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	$ 377,000,000
Option Contracts, Power [Member] | 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	61.00%
Option Contracts, Power [Member] | 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	50.00%
Option Contracts, Power [Member] | 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	57.00%
Option Contracts, Power [Member] | 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	310.00%
Option Contracts, Power [Member] | 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	33.00%
Option Contracts, Power [Member] | 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	119.00%
Option Contracts, Power [Member] | Derivative Financial Instruments, Assets [Member] | 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	$ 48,000,000
Option Contracts, Primarily Gas [Member] | 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	61.00%
Option Contracts, Primarily Gas [Member] | 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	50.00%
Option Contracts, Primarily Gas [Member] | 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	57.00%
Option Contracts, Primarily Gas [Member] | 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	233.00%
Option Contracts, Primarily Gas [Member] | 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	20.00%
Option Contracts, Primarily Gas [Member] | 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	50.00%
Option Contracts, Primarily Gas [Member] | Derivative Financial Instruments, Assets [Member] | 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	$ 100,000,000
Full Requirements and Unit Contingent Contracts [Member] | 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	340
Full Requirements and Unit Contingent Contracts [Member] | 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	(2)
Full Requirements and Unit Contingent Contracts [Member] | 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	$ 67
Full Requirements and Unit Contingent Contracts [Member] | 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	66.00%
Full Requirements and Unit Contingent Contracts [Member] | 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] | 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	4.00%
Full Requirements and Unit Contingent Contracts [Member] | Derivative Financial Instruments, Assets [Member] | 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	$ 674,000,000
Forward contracts - Other | Derivative Financial Instruments, Assets [Member] | Forward contracts - Other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets, Fair Value Disclosure	163,000,000
Forward contracts - Other | Derivative Financial Instruments, Assets [Member] | 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	63,000,000
Forward contracts - Congestion | 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	32
Forward contracts - Congestion | 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	(30)
Forward contracts - Congestion | 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] | 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	470,000,000
Derivative Financial Instruments, Liabilities [Member] | Forward contracts - Gas [Member] | 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	77,000,000
Derivative Financial Instruments, Liabilities [Member] | Option Contracts, Power [Member] | 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	5,000,000
Derivative Financial Instruments, Liabilities [Member] | Option Contracts, Primarily Gas [Member] | 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	97,000,000
Derivative Financial Instruments, Liabilities [Member] | Full Requirements and Unit Contingent Contracts [Member] | 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	146,000,000
Derivative Financial Instruments, Liabilities [Member] | Forward contracts - Other | Forward contracts - Other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, Fair Value Disclosure	123,000,000
Derivative Financial Instruments, Liabilities [Member] | Forward contracts - Other | 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	$ 56,000,000