Derivatives - Schedule of Pre-Tax Effects of Cash Flow and Fair Value Hedging on Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Derivative [Line Items]
Depreciation and amortization	$ 892	$ 871
Total interest expense, net of amounts capitalized	(462)	(450)
Total other income (expense), net	145	58
Natural gas
Derivative [Line Items]
Total cost of sales	1,095	583
Other Income (Expense)
Derivative [Line Items]
Amount excluded from effectiveness testing recognized in earnings	(4)	0
Cash Flow Hedging | Energy-related derivatives | Cost of Sales
Derivative [Line Items]
Gain (loss) on hedges	9	(3)
Cash Flow Hedging | Energy-related derivatives | Depreciation and Amortization
Derivative [Line Items]
Gain (loss) on hedges	2	3
Cash Flow Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(7)	(7)
Cash Flow Hedging | Foreign currency derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(6)	(6)
Cash Flow Hedging | Foreign currency derivatives | Other Income (Expense)
Derivative [Line Items]
Gain (loss) on hedges	(25)	(60)
Fair Value Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(123)	(10)
Fair Value Hedging | Foreign currency derivatives | Other Income (Expense)
Derivative [Line Items]
Gain (loss) on hedges	(24)	0
SOUTHERN POWER CO
Derivative [Line Items]
Depreciation and amortization	120	119
Total interest expense, net of amounts capitalized	(37)	(38)
Total other income (expense), net	2	7
SOUTHERN POWER CO | Cash Flow Hedging | Energy-related derivatives | Depreciation and Amortization
Derivative [Line Items]
Gain (loss) on hedges	2	3
SOUTHERN POWER CO | Cash Flow Hedging | Foreign currency derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(6)	(6)
SOUTHERN POWER CO | Cash Flow Hedging | Foreign currency derivatives | Other Income (Expense)
Derivative [Line Items]
Gain (loss) on hedges	(25)	(60)
SOUTHERN Co GAS
Derivative [Line Items]
Depreciation and amortization	137	130
Total interest expense, net of amounts capitalized	(61)	(60)
Total other income (expense), net	16	(63)
SOUTHERN Co GAS | Natural gas
Derivative [Line Items]
Total cost of sales	1,095	583
SOUTHERN Co GAS | Cash Flow Hedging | Energy-related derivatives | Cost of Sales
Derivative [Line Items]
Gain (loss) on hedges	9	0
SOUTHERN Co GAS | Cash Flow Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(1)	0
SOUTHERN Co GAS | Fair Value Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	$ (36)	$ 0