LEASES - Undiscounted Cash Flows to be Received Under Tolling Arrangements Accounted for as Sales-type Leases (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Sales-type and Direct Financing Leases, Lease Receivable, Fiscal Year Maturity [Abstract]
2025	$ 52
2026	38
2027	37
2028	36
2029	35
Thereafter	302
Total undiscounted cash flows	500
Lease receivable	297
Difference between undiscounted cash flows and discounted cash flows	203
Mississippi Power
Sales-type and Direct Financing Leases, Lease Receivable, Fiscal Year Maturity [Abstract]
2025	24
2026	23
2027	22
2028	21
2029	20
Thereafter	132
Total undiscounted cash flows	242
Lease receivable	139
Difference between undiscounted cash flows and discounted cash flows	103
Southern Power
Sales-type and Direct Financing Leases, Lease Receivable, Fiscal Year Maturity [Abstract]
2025	15
2026	15
2027	15
2028	15
2029	15
Thereafter	170
Total undiscounted cash flows	245
Lease receivable	158
Difference between undiscounted cash flows and discounted cash flows	87
Other Property and Investments \| Mississippi Power
Sales-type and Direct Financing Leases, Lease Receivable, Fiscal Year Maturity [Abstract]
Lease receivable	129	$ 138
Other current assets \| Mississippi Power
Sales-type and Direct Financing Leases, Lease Receivable, Fiscal Year Maturity [Abstract]
Lease receivable	10	10
Other current assets \| Southern Power
Sales-type and Direct Financing Leases, Lease Receivable, Fiscal Year Maturity [Abstract]
Lease receivable	15	15
Net investment in sales-type leases \| Southern Power
Sales-type and Direct Financing Leases, Lease Receivable, Fiscal Year Maturity [Abstract]
Lease receivable	$ 143	$ 148

Present value of lease payments not yet received by lessor and amount expected to be derived from underlying asset, following end of lease term guaranteed by lessee or other third party unrelated to lessor, from sales-type and direct financing leases.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479773/842-30-50-6

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479773/842-30-50-10

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Amount of undiscounted cash flows to be received by lessor for sales-type and direct financing leases.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479773/842-30-50-10

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Amount of undiscounted cash flows to be received by lessor for sales-type and direct financing leases in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of undiscounted cash flows to be received by lessor for sales-type and direct financing leases in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of undiscounted cash flows to be received by lessor for sales-type and direct financing leases in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of undiscounted cash flows to be received by lessor for sales-type and direct financing leases after fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of undiscounted cash flows to be received by lessor for sales-type and direct financing leases in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of undiscounted cash flows to be received by lessor for sales-type and direct financing leases in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of undiscounted lease receivable in excess of discounted receivable for sales-type and direct financing leases.

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