Fair Value (Unobservable Inputs related to Level 3 Assets and Liabilities) (Details) $ in Millions	Dec. 31, 2023 USD ($) $ / MWh $ / MMBTU	Dec. 31, 2022 USD ($) $ / MWh $ / MMBTU
Unobservable Input Valuation Techniques [Line Items]
Derivative Assets	$ 1,197	$ 1,922
Derivative Liabilities	(1,172)	(2,169)
Natural Gas
Unobservable Input Valuation Techniques [Line Items]
Derivative Assets	637	744
Derivative Liabilities	(615)	(1,018)
Electricity
Unobservable Input Valuation Techniques [Line Items]
Derivative Assets	421	963
Derivative Liabilities	$ (388)	$ (935)
Level 3 | Discounted Cash Flow | Forward basis price | Natural Gas | Minimum
Unobservable Input Valuation Techniques [Line Items]
Forward basis price | $ / MMBTU	(1.57)	(1.91)
Level 3 | Discounted Cash Flow | Forward basis price | Natural Gas | Maximum
Unobservable Input Valuation Techniques [Line Items]
Forward basis price | $ / MMBTU	6.27	39.94
Level 3 | Discounted Cash Flow | Forward basis price | Natural Gas | Weighted Average
Unobservable Input Valuation Techniques [Line Items]
Forward basis price | $ / MMBTU	(0.08)	0.18
Level 3 | Discounted Cash Flow | Forward basis price | Electricity | Minimum
Unobservable Input Valuation Techniques [Line Items]
Forward basis price | $ / MWh	(18.49)	(29.41)
Level 3 | Discounted Cash Flow | Forward basis price | Electricity | Maximum
Unobservable Input Valuation Techniques [Line Items]
Forward basis price | $ / MWh	15.47	15.00
Level 3 | Discounted Cash Flow | Forward basis price | Electricity | Weighted Average
Unobservable Input Valuation Techniques [Line Items]
Forward basis price | $ / MWh	(3.99)	(3.04)
Recurring | Level 3
Unobservable Input Valuation Techniques [Line Items]
Derivative Assets	$ 350	$ 390
Recurring | Level 3 | Natural Gas
Unobservable Input Valuation Techniques [Line Items]
Derivative Assets	179	135
Derivative Liabilities	(157)	(390)
Recurring | Level 3 | Electricity
Unobservable Input Valuation Techniques [Line Items]
Derivative Assets	163	243
Derivative Liabilities	$ (116)	$ (276)