Fair Value (Unobservable Inputs related to Level 3 Assets and Liabilities) (Details) $ in Millions	Jun. 30, 2023 USD ($) $ / MMBTU $ / MWh	Dec. 31, 2022 USD ($) $ / MWh $ / MMBTU
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	$ 1,356	$ 1,922
Derivative Liabilities	(1,429)	(2,169)
Natural gas
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	501	744
Derivative Liabilities	(583)	(1,018)
Electricity
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	497	963
Derivative Liabilities	$ (487)	$ (935)
Level 3 | Natural gas | Forward basis price | Minimum | Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price | $ / MMBTU	(1.62)	(1.91)
Level 3 | Natural gas | Forward basis price | Maximum | Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price | $ / MMBTU	4.59	39.94
Level 3 | Natural gas | Forward basis price | Weighted Average | Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price | $ / MMBTU	(0.07)	0.18
Level 3 | Electricity | Forward basis price | Minimum | Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price | $ / MWh	(20.34)	(29.41)
Level 3 | Electricity | Forward basis price | Maximum | Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price | $ / MWh	12.99	15.00
Level 3 | Electricity | Forward basis price | Weighted Average | Discounted Cash Flow
Unobservable Inputs Valuation Techniques [Line Items]
Forward basis price | $ / MWh	(3.43)	(3.04)
Recurring | Level 3
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	$ 338	$ 390
Recurring | Level 3 | Natural gas
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	167	135
Derivative Liabilities	(221)	(390)
Recurring | Level 3 | Electricity
Unobservable Inputs Valuation Techniques [Line Items]
Derivative Assets	149	243
Derivative Liabilities	$ (153)	$ (276)