INCOME TAXES - Amortization of Deferred Credits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Income Tax Disclosure [Line Items]
Amortization of investment tax credits	$ 84	$ 109	$ 84
Traditional Electric Operating Companies
Income Tax Disclosure [Line Items]
Amortization of investment tax credits	0
Southern Company Gas
Income Tax Disclosure [Line Items]
Amortization of investment tax credits	0	0	0
Southern Power
Income Tax Disclosure [Line Items]
Amortization of investment tax credits	$ 58	$ 58	$ 58