CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2024 USD ($) investor	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Redeemable Noncontrolling Interest [Line Items]
Total assets	$ 145,180	$ 139,331	$ 134,891
Liabilities	108,506	104,106
Equity investments in unconsolidated subsidiaries	1,416	1,368
Earnings from equity method investments	139	144	151
Southern Power
Redeemable Noncontrolling Interest [Line Items]
Total assets	12,653	12,761
Liabilities	5,971	6,063
Proceeds from sale of equity method investments	$ 50	38
Southern Power | SP Solar Holdings I, LP
Redeemable Noncontrolling Interest [Line Items]
Sale of equity interest in limited partnership	33.00%
Southern Company Gas
Redeemable Noncontrolling Interest [Line Items]
Total assets	$ 26,177	25,083	24,621
Liabilities	15,181	14,280
Equity investments in unconsolidated subsidiaries	1,279	1,235
Earnings from equity method investments	146	140	148
Southern Company Gas | SNG
Redeemable Noncontrolling Interest [Line Items]
Equity investments in unconsolidated subsidiaries	1,245	1,202
Earnings from equity method investments	$ 146	139	$ 146
Wholly Owned Subsidiary Of Southern Power | Southern Power | SP Solar Holdings I, LP
Redeemable Noncontrolling Interest [Line Items]
Ownership interest	66.00%
Wholly Owned Subsidiary Of Southern Power | Southern Power | SP Wind
Redeemable Noncontrolling Interest [Line Items]
Ownership interest	100.00%
SP Solar Holdings I, LP | Southern Power
Redeemable Noncontrolling Interest [Line Items]
Distribution made to limited partner, cash distributions paid, percentage	67.00%
SP Solar Holdings I, LP | Global Atlantic
Redeemable Noncontrolling Interest [Line Items]
Distribution made to limited partner, cash distributions paid, percentage	33.00%
SP Wind | Southern Power
Redeemable Noncontrolling Interest [Line Items]
Distribution made to limited partner, cash distributions paid, percentage	60.00%
Number of financial investors | investor	3
SP Wind | Financial Investors
Redeemable Noncontrolling Interest [Line Items]
Distribution made to limited partner, cash distributions paid, percentage	40.00%
General Partner | Wholly Owned Subsidiary Of Southern Power | Southern Power | SP Solar Holdings I, LP
Redeemable Noncontrolling Interest [Line Items]
Ownership interest	1.00%
Variable Interest Entity, Primary Beneficiary | SP Solar Holdings I, LP | Southern Power
Redeemable Noncontrolling Interest [Line Items]
Total assets	$ 5,400	5,600
Liabilities	372	399
Noncontrolling interests related to other partners' interest	1,000
Variable Interest Entity, Primary Beneficiary | SP Wind | Southern Power
Redeemable Noncontrolling Interest [Line Items]
Total assets	2,000	2,100
Liabilities	177	187
Noncontrolling interests related to other partners' interest	35	38
Variable Interest Entity, Primary Beneficiary | Other Variable Interest Entities | Southern Power
Redeemable Noncontrolling Interest [Line Items]
Total assets	1,600	1,700
Liabilities	224	230
Noncontrolling interests related to other partners' interest	$ 691	$ 761