Fair Value Measurements - Schedule of Fair Value of the Level 3 Assets and Liabilities by Major Contract Type and the Significant Unobservable Inputs Used in the Valuations (Details)	12 Months Ended
	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative Asset, Statement of Financial Position, Extensible Enumeration Not Disclosed Flag	Assets
Derivative Liability Statement of Financial Position Extensible Enumeration Not Disclosed Flag	Liabilities
Level 3
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Assets	$ 841,000,000	$ 630,000,000
Liabilities	(1,593,000,000)	(1,674,000,000)
Total, Net	(752,000,000)	(1,044,000,000)
Electricity purchases and sales | Income Approach | Level 3
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Assets	606,000,000	449,000,000
Liabilities	(1,399,000,000)	(1,273,000,000)
Total, Net	(793,000,000)	(824,000,000)
Electricity purchases and sales | Minimum | Income Approach | Level 3 | Hourly price curve shape
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input amount	0	0
Electricity purchases and sales | Minimum | Income Approach | Level 3 | Illiquid delivery periods for hub power prices and heat rates
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input amount	25	30
Electricity purchases and sales | Minimum | Income Approach | Level 3 | Market Heat Rates
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input amount	30
Electricity purchases and sales | Maximum | Income Approach | Level 3 | Hourly price curve shape
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input amount	95	85
Electricity purchases and sales | Maximum | Income Approach | Level 3 | Illiquid delivery periods for hub power prices and heat rates
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input amount	140	110
Electricity purchases and sales | Maximum | Income Approach | Level 3 | Market Heat Rates
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input amount	150
Electricity purchases and sales | Arithmetic Average | Income Approach | Level 3 | Hourly price curve shape
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input amount	48	44
Electricity purchases and sales | Arithmetic Average | Income Approach | Level 3 | Illiquid delivery periods for hub power prices and heat rates
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input amount	83	71
Electricity purchases and sales | Arithmetic Average | Income Approach | Level 3 | Market Heat Rates
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input amount	90
Options | Option Pricing Model | Level 3
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Assets	6,000,000	1,000,000
Liabilities	(139,000,000)	(237,000,000)
Total, Net	$ (133,000,000)	$ (236,000,000)
Options | Minimum | Option Pricing Model | Level 3 | Natural gas to power correlation
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input	0.10	0.10
Options | Minimum | Option Pricing Model | Level 3 | Power and natural gas volatility
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input	0.05	0.10
Options | Maximum | Option Pricing Model | Level 3 | Natural gas to power correlation
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input	1	1
Options | Maximum | Option Pricing Model | Level 3 | Power and natural gas volatility
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input	7.10	8.70
Options | Arithmetic Average | Option Pricing Model | Level 3 | Natural gas to power correlation
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input	0.55	0.55
Options | Arithmetic Average | Option Pricing Model | Level 3 | Power and natural gas volatility
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input	3.58	4.41
Financial transmission rights/Congestion revenue rights | Market Approach | Level 3
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Assets	$ 190,000,000	$ 157,000,000
Liabilities	(25,000,000)	(34,000,000)
Total, Net	165,000,000	123,000,000
Financial transmission rights/Congestion revenue rights | Minimum | Market Approach | Level 3 | Illiquid price differences between settlement points
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input amount	(35)	(85)
Financial transmission rights/Congestion revenue rights | Maximum | Market Approach | Level 3 | Illiquid price differences between settlement points
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input amount	20	25
Financial transmission rights/Congestion revenue rights | Arithmetic Average | Market Approach | Level 3 | Illiquid price differences between settlement points
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input amount	(8)	(30)
Natural gas | Income Approach | Level 3
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Assets	29,000,000	9,000,000
Liabilities	(30,000,000)	(112,000,000)
Total, Net	(1,000,000)	(103,000,000)
Natural gas | Minimum | Income Approach | Level 3 | Natural gas basis
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input amount	0	0
Natural gas | Minimum | Income Approach | Level 3 | Illiquid delivery periods
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input amount	0	0
Natural gas | Maximum | Income Approach | Level 3 | Natural gas basis
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input amount	10	15
Natural gas | Maximum | Income Approach | Level 3 | Illiquid delivery periods
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input amount	5	5
Natural gas | Arithmetic Average | Income Approach | Level 3 | Natural gas basis
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input amount	5	6
Natural gas | Arithmetic Average | Income Approach | Level 3 | Illiquid delivery periods
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative asset (liability), measurement input amount	2	4
Other | Level 3
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Assets	10,000,000	14,000,000
Liabilities	0	(18,000,000)
Total, Net	$ 10,000,000	$ (4,000,000)