Fair Value (Unobservable Inputs related to Level 3 Assets and Liabilities) (Details) $ in Millions	Sep. 30, 2024 USD ($) $ / MMBTU $ / MWh	Dec. 31, 2023 USD ($) $ / MMBTU $ / MWh
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	$ 684	$ 1,197
Derivative Liabilities	(622)	(1,172)
Natural gas
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	399	637
Derivative Liabilities	(377)	(615)
Electricity
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	191	421
Derivative Liabilities	$ (171)	$ (388)
Level 3 | Natural gas | Forward basis price | Minimum | Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price | $ / MMBTU	(1.28)	(1.57)
Level 3 | Natural gas | Forward basis price | Maximum | Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price | $ / MMBTU	2.44	6.27
Level 3 | Natural gas | Forward basis price | Weighted Average | Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price | $ / MMBTU	(0.13)	(0.08)
Level 3 | Electricity | Forward basis price | Minimum | Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price | $ / MWh	(18.51)	(18.49)
Level 3 | Electricity | Forward basis price | Maximum | Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price | $ / MWh	16.65	15.47
Level 3 | Electricity | Forward basis price | Weighted Average | Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price | $ / MWh	(3.38)	(3.99)
Recurring | Level 3
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	$ 228	$ 350
Recurring | Level 3 | Natural gas
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	108	179
Derivative Liabilities	(113)	(157)
Recurring | Level 3 | Electricity
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	98	163
Derivative Liabilities	$ (69)	$ (116)