SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - (Financial Assets Measured at Amortized Cost – Credit Losses) (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
Public Utility, Property, Plant and Equipment [Line Items]
Credit losses	$ 89	$ 100
Regulatory assets	15,722		$ 15,981
Regulatory Balancing Accounts Receivable
Public Utility, Property, Plant and Equipment [Line Items]
Total regulatory balancing accounts	5,025		6,300
FERC TO rates
Public Utility, Property, Plant and Equipment [Line Items]
Regulatory assets	88		92
Residential uncollectibles balancing accounts | Regulatory Balancing Accounts Receivable
Public Utility, Property, Plant and Equipment [Line Items]
Total regulatory balancing accounts	60		$ 278
Decrease in regulatory balancing accounts	$ 278