LEASES - Undiscounted Cash Flows to be Received Under Tolling Arrangements Accounted for as Sales-type Leases (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Sales-type and Direct Financing Leases, Lease Receivable, Fiscal Year Maturity [Abstract]
2024	$ 38
2025	37
2026	36
2027	35
2028	34
Thereafter	330
Total undiscounted cash flows	510
Lease receivable	311
Difference between undiscounted cash flows and discounted cash flows	199
Other Property and Investments \| Mississippi Power
Sales-type and Direct Financing Leases, Lease Receivable, Fiscal Year Maturity [Abstract]
2024	23
2025	22
2026	21
2027	20
2028	19
Thereafter	145
Total undiscounted cash flows	250
Lease receivable	148
Difference between undiscounted cash flows and discounted cash flows	102
Other Current Assets and Net Investment in Sales-type Lease \| Southern Power
Sales-type and Direct Financing Leases, Lease Receivable, Fiscal Year Maturity [Abstract]
2024	15
2025	15
2026	15
2027	15
2028	15
Thereafter	185
Total undiscounted cash flows	260
Lease receivable	163
Difference between undiscounted cash flows and discounted cash flows	97
Other current assets \| Southern Power
Sales-type and Direct Financing Leases, Lease Receivable, Fiscal Year Maturity [Abstract]
Lease receivable	148	$ 15
Net investment in sales-type leases \| Southern Power
Sales-type and Direct Financing Leases, Lease Receivable, Fiscal Year Maturity [Abstract]
Lease receivable	$ 15	$ 154

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 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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