Long-Term and Short-Term Debt (Schedule of Debt) (Parenthetical) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Letter of Credit
Debt Instrument [Line Items]
Debt instrument, face amount	$ 68
First Mortgage Bonds | Minimum [Member] | DESC
Debt Instrument [Line Items]
Debt Instrument, Maturity Year	2028
Debt instrument, interest rate	2.30%
First Mortgage Bonds | Maximum [Member] | DESC
Debt Instrument [Line Items]
Debt Instrument, Maturity Year	2065
Debt instrument, interest rate	6.625%
Tax Exempt Financings Variable Rate Due 2038 | DESC
Debt Instrument [Line Items]
Debt Instrument, Maturity Year	2038
Tax Exempt Financings Variable Rate Due 2038 | Genco
Debt Instrument [Line Items]
Debt Instrument, Maturity Year	2038
Tax Exempt Financings 3.625% and 4.00% Due 2028 and 2033 | Minimum [Member] | DESC
Debt Instrument [Line Items]
Debt Instrument, Maturity Year	2028
Debt instrument, interest rate	3.625%
Tax Exempt Financings 3.625% and 4.00% Due 2028 and 2033 | Maximum [Member] | DESC
Debt Instrument [Line Items]
Debt Instrument, Maturity Year	2033
Debt instrument, interest rate	4.00%
3.05% Affiliated Note Due 2024 | Genco
Debt Instrument [Line Items]
Debt Instrument, Maturity Year	2024
Debt instrument, interest rate	3.05%