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, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Derivative [Line Items]
Total cost of sales	$ 231	$ 144	$ 814	$ 583
Depreciation and amortization	891	873	1,762	1,730
Total interest expense, net of amounts capitalized	(450)	(444)	(901)	(900)
Total other income (expense), net	108	101	167	204
Cash Flow Hedging | Energy-related derivatives | Cost of Sales
Derivative [Line Items]
Gain (loss) on hedges	1	(1)	(2)	(8)
Cash Flow Hedging | Energy-related derivatives | Depreciation and Amortization
Derivative [Line Items]
Gain (loss) on hedges	1	(1)	4	(2)
Cash Flow Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(7)	(6)	(14)	(13)
Cash Flow Hedging | Foreign currency derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(6)	(6)	(12)	(12)
Cash Flow Hedging | Foreign currency derivatives | Other Income (Expense)
Derivative [Line Items]
Gain (loss) on hedges	17	27	(43)	(4)
Fair Value Hedging | Interest rate derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(3)	1	(12)	30
SOUTHERN POWER CO
Derivative [Line Items]
Depreciation and amortization	132	121	251	239
Total interest expense, net of amounts capitalized	(37)	(38)	(75)	(77)
Total other income (expense), net	1	1	8	4
SOUTHERN POWER CO | Cash Flow Hedging | Energy-related derivatives | Depreciation and Amortization
Derivative [Line Items]
Gain (loss) on hedges	1	(1)	4	(2)
SOUTHERN POWER CO | Cash Flow Hedging | Foreign currency derivatives | Interest Expense
Derivative [Line Items]
Gain (loss) on hedges	(6)	(6)	(12)	(12)
SOUTHERN POWER CO | Cash Flow Hedging | Foreign currency derivatives | Other Income (Expense)
Derivative [Line Items]
Gain (loss) on hedges	$ 17	$ 27	$ (43)	$ (4)