Fair Value (Unobservable Inputs Related to Level 3 Assets and Liabilities) (Details) $ in Millions	Jun. 30, 2026 USD ($) $ / MWh $ / MMBTU	Dec. 31, 2025 USD ($) $ / MMBTU $ / MWh
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	$ 1,001	$ 707
Derivative Liabilities	(941)	(597)
Natural gas
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	293	372
Derivative Liabilities	(313)	(329)
Electricity
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	608	275
Derivative Liabilities	(578)	(235)
Level 3
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	143	153
Level 3 \| Natural gas
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	94	109
Derivative Liabilities	$ (75)	$ (82)
Level 3 \| Natural gas \| Forward basis price \| Minimum \| Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price \| $ / MMBTU	(1.11)	(1.35)
Level 3 \| Natural gas \| Forward basis price \| Maximum \| Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price \| $ / MMBTU	4.61	9.33
Level 3 \| Natural gas \| Forward basis price \| Weighted Average \| Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price \| $ / MMBTU	(0.17)	(0.13)
Level 3 \| Electricity
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	$ 26	$ 33
Derivative Liabilities	$ (170)	$ (52)
Level 3 \| Electricity \| Forward basis price \| Minimum \| Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price \| $ / MWh	(55.16)	(21.82)
Level 3 \| Electricity \| Forward basis price \| Maximum \| Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price \| $ / MWh	55.25	17.79
Level 3 \| Electricity \| Forward basis price \| Weighted Average \| Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price \| $ / MWh	(13.74)	(5.58)