Derivatives - Schedule of Pre-Tax Effects of Cash Flow and Fair Value Hedging on Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Derivative [Line Items]
Depreciation and amortization	$ 913	$ 891	$ 1,805	$ 1,762
Total interest expense, net of amounts capitalized	(488)	(450)	(950)	(901)
Total other income (expense), net	139	101	283	160
Natural gas
Derivative [Line Items]
Total cost of sales	452	231	1,546	814
Other Income (Expense)
Derivative [Line Items]
Amount excluded from effectiveness testing recognized in earnings	7	0	3	0
Cash Flow Hedging | Energy-related derivatives | Cost of Sales
Derivative [Line Items]
Gain (loss) on hedges	10	1	18	(2)
Cash Flow Hedging | Energy-related derivatives | Depreciation and Amortization
Derivative [Line Items]
Gain (loss) on hedges	4	1	6	4
Cash Flow Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(6)	(7)	(13)	(14)
Cash Flow Hedging | Foreign currency derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(7)	(6)	(13)	(12)
Cash Flow Hedging | Foreign currency derivatives | Other Income (Expense)
Derivative [Line Items]
Gain (loss) on hedges	(73)	17	(97)	(43)
Fair Value Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(76)	(3)	(198)	(12)
Fair Value Hedging | Foreign currency derivatives | Other Income (Expense)
Derivative [Line Items]
Gain (loss) on hedges	(96)	0	(121)	0
SOUTHERN POWER CO
Derivative [Line Items]
Depreciation and amortization	131	132	251	251
Total interest expense, net of amounts capitalized	(36)	(37)	(73)	(75)
Total other income (expense), net	1	1	3	8
SOUTHERN POWER CO | Cash Flow Hedging | Energy-related derivatives | Depreciation and Amortization
Derivative [Line Items]
Gain (loss) on hedges	4	1	6	4
SOUTHERN POWER CO | Cash Flow Hedging | Foreign currency derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(7)	(6)	(13)	(12)
SOUTHERN POWER CO | Cash Flow Hedging | Foreign currency derivatives | Other Income (Expense)
Derivative [Line Items]
Gain (loss) on hedges	(73)	17	(97)	(43)
SOUTHERN Co GAS
Derivative [Line Items]
Depreciation and amortization	138	133	275	263
Total interest expense, net of amounts capitalized	(61)	(59)	(122)	(118)
Total other income (expense), net	16	(14)	32	(78)
SOUTHERN Co GAS | Natural gas
Derivative [Line Items]
Total cost of sales	452	231	1,546	814
SOUTHERN Co GAS | Cash Flow Hedging | Energy-related derivatives | Cost of Sales
Derivative [Line Items]
Gain (loss) on hedges	10	0	18	(2)
SOUTHERN Co GAS | Cash Flow Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(1)	(1)	(1)	(1)
SOUTHERN Co GAS | Fair Value Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	$ (22)	$ 4	$ (57)	$ 4