Consolidated Entities and Equity Method Investments - Narrative (Details) $ in Millions	3 Months Ended	9 Months Ended
	Mar. 31, 2023 USD ($)	Sep. 30, 2023 USD ($) investor	Dec. 31, 2022 USD ($)
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries		$ 1,376	$ 1,443
Assets		138,321	134,891
Liabilities		103,017	100,359
Southern Holdings Company
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries		126	112
SOUTHERN POWER CO
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries		0	49
Assets		13,090	13,081
Liabilities		$ 6,247	6,165
Proceeds from sale of equity method investments	$ 50
SP Solar Holdings I, LP | SOUTHERN POWER CO
Schedule of Equity Method Investments [Line Items]
Distribution made to limited partner, cash distributions paid, percentage		67.00%
SP Solar Holdings I, LP | Global Atlantic
Schedule of Equity Method Investments [Line Items]
Distribution made to limited partner, cash distributions paid, percentage		33.00%
Variable Interest Entity, Primary Beneficiary | SP Solar Holdings I, LP | SOUTHERN POWER CO
Schedule of Equity Method Investments [Line Items]
Assets		$ 5,800	5,900
Liabilities		400	400
Noncontrolling interests related to other partners' interests		1,100
Variable Interest Entity, Primary Beneficiary | SP Wind | SOUTHERN POWER CO
Schedule of Equity Method Investments [Line Items]
Assets		2,200	2,200
Liabilities		184	169
Noncontrolling interests related to other partners' interests		$ 38	39
Distribution made to limited partner, cash distributions paid, percentage		60.00%
Number of financial investors | investor		3
Variable Interest Entity, Primary Beneficiary | SP Wind | Financial Investors
Schedule of Equity Method Investments [Line Items]
Distribution made to limited partner, cash distributions paid, percentage		40.00%
Variable Interest Entity, Primary Beneficiary | Other Variable Interest Entities | SOUTHERN POWER CO
Schedule of Equity Method Investments [Line Items]
Assets		$ 1,700	1,800
Liabilities		200	200
Noncontrolling interests related to other partners' interests		$ 800	$ 800