Fair Value (Unobservable Inputs related to Level 3 Assets and Liabilities) (Details) $ in Millions	Mar. 31, 2025 USD ($) $ / MWh $ / MMBTU	Dec. 31, 2024 USD ($) $ / MMBTU $ / MWh
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	$ 837	$ 694
Derivative Liabilities	(758)	(605)
Natural gas
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	461	428
Derivative Liabilities	(395)	(410)
Electricity
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	304	187
Derivative Liabilities	$ (310)	$ (150)
Level 3 | Natural gas | Forward basis price | Minimum | Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price | $ / MMBTU	(1.36)	(1.24)
Level 3 | Natural gas | Forward basis price | Maximum | Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price | $ / MMBTU	2.52	9.96
Level 3 | Natural gas | Forward basis price | Weighted Average | Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price | $ / MMBTU	(0.04)	(0.05)
Level 3 | Electricity | Forward basis price | Minimum | Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price | $ / MWh	(17.35)	(16.34)
Level 3 | Electricity | Forward basis price | Maximum | Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price | $ / MWh	18.38	17.28
Level 3 | Electricity | Forward basis price | Weighted Average | Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price | $ / MWh	(4.30)	(2.74)
Recurring | Level 3
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	$ 114	$ 166
Recurring | Level 3 | Natural gas
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	98	105
Derivative Liabilities	(98)	(123)
Recurring | Level 3 | Electricity
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	13	51
Derivative Liabilities	$ (104)	$ (27)