Derivatives - Schedule of Pre-Tax Effects of Cash Flow and Fair Value Hedging on Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Derivative [Line Items]
Depreciation and amortization	$ 1,111	$ 892
Total interest expense, net of amounts capitalized	(582)	(462)
Total other income (expense), net	147	145
Natural gas
Derivative [Line Items]
Total cost of sales	898	1,095
Other Income (Expense)
Derivative [Line Items]
Amount excluded from effectiveness testing recognized in earnings	28	(4)
Cash Flow Hedging | Energy-related derivatives | Cost of Sales
Derivative [Line Items]
Gain (loss) on hedges	(20)	9
Cash Flow Hedging | Energy-related derivatives | Depreciation and Amortization
Derivative [Line Items]
Gain (loss) on hedges	(9)	2
Cash Flow Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(4)	(7)
Cash Flow Hedging | Foreign currency derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(3)	(6)
Cash Flow Hedging | Foreign currency derivatives | Other Income (Expense)
Derivative [Line Items]
Gain (loss) on hedges	10	(25)
Fair Value Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	43	(123)
Fair Value Hedging | Foreign currency derivatives | Other Income (Expense)
Derivative [Line Items]
Gain (loss) on hedges	(2)	(24)
SOUTHERN POWER CO
Derivative [Line Items]
Depreciation and amortization	128	120
Total interest expense, net of amounts capitalized	(33)	(37)
Total other income (expense), net	2	2
SOUTHERN POWER CO | Cash Flow Hedging | Energy-related derivatives | Depreciation and Amortization
Derivative [Line Items]
Gain (loss) on hedges	(9)	2
SOUTHERN POWER CO | Cash Flow Hedging | Foreign currency derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(3)	(6)
SOUTHERN POWER CO | Cash Flow Hedging | Foreign currency derivatives | Other Income (Expense)
Derivative [Line Items]
Gain (loss) on hedges	10	(25)
SOUTHERN Co GAS
Derivative [Line Items]
Depreciation and amortization	141	137
Total interest expense, net of amounts capitalized	(76)	(61)
Total other income (expense), net	14	16
SOUTHERN Co GAS | Natural gas
Derivative [Line Items]
Total cost of sales	898	1,095
SOUTHERN Co GAS | Cash Flow Hedging | Energy-related derivatives | Cost of Sales
Derivative [Line Items]
Gain (loss) on hedges	(20)	9
SOUTHERN Co GAS | Cash Flow Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(1)	(1)
SOUTHERN Co GAS | Fair Value Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	$ 13	$ (36)