Derivative Instruments (Significant Unobservable Inputs) (Details) - Level 3	3 Months Ended
	Mar. 31, 2022 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets, Fair Value Disclosure	$ 1,968,000,000
Financial and Nonfinancial Liabilities, Fair Value Disclosure	(3,040,000,000)
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)	223
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)	(4)
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)	43
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	294,000,000
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)	23
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)	2
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)	4
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	206,000,000
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)	21
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)	(12)
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	$ 23,000,000
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	87.00%
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	37.00%
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	53.00%
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	242.00%
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	18.00%
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	61.00%
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	$ 88,000,000
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	87.00%
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	37.00%
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	53.00%
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	242.00%
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	18.00%
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	$ 1,076,000,000
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)	386
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)	3
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)	$ 78
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	56.00%
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	2.00%
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	$ 35,000,000
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	246,000,000
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	(450,000,000)
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	(180,000,000)
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	(8,000,000)
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	(11,000,000)
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	(966,000,000)
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	(1,285,000,000)
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	$ (140,000,000)