DERIVATIVES - Pre-Tax Effects of Derivatives Designated as Hedges on Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Depreciation and amortization	$ 3,663	$ 3,565	$ 3,518
Interest expense, net of amounts capitalized	(2,022)	(1,837)	(1,821)
Other income (expense), net	500	456	336
Energy-related derivatives | Cost of Sales | Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative	37	17	(8)
Energy-related derivatives | Depreciation and Amortization | Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative	(5)	9	(3)
Interest rate derivatives | Interest Expense | Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative	(25)	(27)	(26)
Interest rate derivatives | Interest Expense | Fair Value Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative	(291)	(30)	27
Foreign currency derivatives | Interest Expense | Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative	(19)	(24)	(23)
Foreign currency derivatives | Other Income (Expense) | Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative	(83)	(104)	114
Gain (loss) on foreign currency fair value hedges	(106)	(63)	0
Amount excluded from effectiveness testing recognized in earnings	24	3	0
Southern Power
Derivative Instruments, Gain (Loss) [Line Items]
Depreciation and amortization	516	517	494
Interest expense, net of amounts capitalized	(138)	(147)	(151)
Other income (expense), net	7	10	19
Southern Power | Energy-related derivatives | Depreciation and Amortization | Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative	(5)	9	(3)
Southern Power | Foreign currency derivatives | Interest Expense | Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative	(19)	(24)	(23)
Southern Power | Foreign currency derivatives | Other Income (Expense) | Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative	(83)	(104)	114
Southern Company Gas
Derivative Instruments, Gain (Loss) [Line Items]
Cost of sales	3,004	1,619	972
Depreciation and amortization	559	536	500
Interest expense, net of amounts capitalized	(263)	(238)	(231)
Other income (expense), net	53	(53)	41
Southern Company Gas | Interest rate derivatives | Interest Expense | Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on hedges	(4)	0	0
Southern Company Gas | Interest rate derivatives | Interest Expense | Fair Value Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on hedges	(86)	0	0
Southern Company Gas | Foreign currency derivatives | Other Income (Expense) | Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative	$ 37	$ 17	$ (8)