Derivatives - Schedule of Pre-Tax Effects of Cash Flow and Fair Value Hedging on Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Derivative [Line Items]
Depreciation and amortization	$ 1,143	$ 922	$ 3,365	$ 2,728
Total interest expense, net of amounts capitalized	(620)	(511)	(1,812)	(1,461)
Total other income (expense), net	141	132	428	414
Utilities Operating Expense, Maintenance and Operations	1,424	1,527	4,352	4,568
Natural gas
Derivative [Line Items]
Total cost of sales	102	294	1,199	1,840
Other Income (Expense)
Derivative [Line Items]
Amount excluded from effectiveness testing recognized in earnings	(27)	(21)	(28)	(17)
Cash Flow Hedging | Energy-related derivatives | Cost of Sales
Derivative [Line Items]
Gain (loss) on hedges	(4)	9	(32)	28
Cash Flow Hedging | Energy-related derivatives | Depreciation and Amortization
Derivative [Line Items]
Gain (loss) on hedges	(5)	(1)	(18)	5
Cash Flow Hedging | Energy-related derivatives | Operating Expense
Derivative [Line Items]
Gain (loss) on hedges	(1)	0	(2)	0
Cash Flow Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(22)	(7)	(31)	(19)
Cash Flow Hedging | Foreign currency derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(3)	(3)	(8)	(16)
Cash Flow Hedging | Foreign currency derivatives | Other Income (Expense)
Derivative [Line Items]
Gain (loss) on hedges	(14)	(32)	(4)	(129)
Fair Value Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(47)	(102)	(50)	(300)
Fair Value Hedging | Foreign currency derivatives | Other Income (Expense)
Derivative [Line Items]
Gain (loss) on hedges	(7)	(59)	19	(180)
SOUTHERN POWER CO
Derivative [Line Items]
Depreciation and amortization	130	133	380	384
Total interest expense, net of amounts capitalized	(32)	(32)	(98)	(105)
Total other income (expense), net	4	3	8	5
Utilities Operating Expense, Maintenance and Operations	104	113	327	332
SOUTHERN POWER CO | Cash Flow Hedging | Energy-related derivatives | Depreciation and Amortization
Derivative [Line Items]
Gain (loss) on hedges	(5)	(1)	(18)	5
SOUTHERN POWER CO | Cash Flow Hedging | Foreign currency derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(3)	(3)	(8)	(16)
SOUTHERN POWER CO | Cash Flow Hedging | Foreign currency derivatives | Other Income (Expense)
Derivative [Line Items]
Gain (loss) on hedges	(14)	(32)	(4)	(129)
SOUTHERN Co GAS
Derivative [Line Items]
Depreciation and amortization	145	140	429	414
Total interest expense, net of amounts capitalized	(77)	(65)	(226)	(187)
Total other income (expense), net	19	15	50	47
Utilities Operating Expense, Maintenance and Operations	264	252	879	824
SOUTHERN Co GAS | Natural gas
Derivative [Line Items]
Total cost of sales	102	294	1,199	1,840
SOUTHERN Co GAS | Cash Flow Hedging | Energy-related derivatives | Cost of Sales
Derivative [Line Items]
Gain (loss) on hedges	(4)	9	(32)	28
SOUTHERN Co GAS | Cash Flow Hedging | Energy-related derivatives | Operating Expense
Derivative [Line Items]
Gain (loss) on hedges	(1)	0	(2)	0
SOUTHERN Co GAS | Cash Flow Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(18)	(2)	(18)	(3)
SOUTHERN Co GAS | Fair Value Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(11)	(30)	(14)	(87)
Traditional Electric Operating Companies | Cash Flow Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	0	0	0	0
Traditional Electric Operating Companies | Fair Value Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	$ 0	$ 0	$ 0	$ 0