INCOME TAXES - Amortization of Deferred Credits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Line Items]
Amortization of deferred investment tax credits	$ 84	$ 84	$ 181
Southern Power
Income Tax Disclosure [Line Items]
Amortization of deferred investment tax credits	$ 58	$ 59	$ 151