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Revenue from Contracts with Customers and Lease Income - Schedule of Lease Income (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Lessor, Lease, Description [Line Items] |  |  |  |
Lease income - interest income on sales-type leases | $ 6 | $ 5 | $ 18 | $ 18
Lease income - operating leases | 38 | 38 | 104 | 108
Variable lease income | 141 | 142 | 347 | 343
Total lease income | 185 | 185 | 469 | 469
ALABAMA POWER CO |  |  |  |
Lessor, Lease, Description [Line Items] |  |  |  |
Lease income - interest income on sales-type leases | 0 | 0 | 0 | 0
Lease income - operating leases | 2 | 2 | 5 | 6
Variable lease income | 0 | 0 | 1 | 0
Total lease income | 2 | 2 | 6 | 6
GEORGIA POWER CO |  |  |  |
Lessor, Lease, Description [Line Items] |  |  |  |
Lease income - interest income on sales-type leases | 0 | 0 | 0 | 0
Lease income - operating leases | 7 | 13 | 22 | 28
Variable lease income | 0 | 0 | 0 | 0
Total lease income | 7 | 13 | 22 | 28
MISSISSIPPI POWER CO |  |  |  |
Lessor, Lease, Description [Line Items] |  |  |  |
Lease income - interest income on sales-type leases | 4 | 3 | 11 | 11
Lease income - operating leases | 1 | 0 | 2 | 2
Variable lease income | 0 | 0 | 0 | 0
Total lease income | 5 | 3 | 13 | 13
SOUTHERN POWER CO |  |  |  |
Lessor, Lease, Description [Line Items] |  |  |  |
Lease income - interest income on sales-type leases | 2 | 2 | 7 | 7
Lease income - operating leases | 37 | 20 | 111 | 63
Variable lease income | 151 | 152 | 375 | 370
Total lease income | 190 | 174 | 493 | 440
SOUTHERN Co GAS |  |  |  |
Lessor, Lease, Description [Line Items] |  |  |  |
Lease income - interest income on sales-type leases | 0 | 0 | 0 | 0
Lease income - operating leases | 9 | 9 | 27 | 27
Variable lease income | 0 | 0 | 0 | 0
Total lease income | $ 9 | $ 9 | $ 27 | $ 27

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- Definition Amount of lease income from operating, direct financing, and sales-type leases. Includes, but is not limited to, variable lease payments, interest income, profit (loss) recognized at commencement, and lease payments paid and payable to lessor. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479773/842-30-50-5 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479773/842-30-50-3 + Details
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- Definition Amount of operating lease income from lease payments and variable lease payments paid and payable to lessor. Includes, but is not limited to, variable lease payments not included in measurement of lease receivable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479773/842-30-50-5 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 270 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6A -Publisher FASB -URI https://asc.fasb.org/1943274/2147482964/270-10-50-6A Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479016/842-30-45-3 + Details
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- Definition Amount of interest income from net investment in sales-type lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 270 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6A -Publisher FASB -URI https://asc.fasb.org/1943274/2147482964/270-10-50-6A Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479773/842-30-50-5 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 30 -Name Accounting Standards Codification -Section 25 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479341/842-30-25-2 + Details
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- Definition Amount of variable lease payments from operating, direct financing, and sales-type leases, excluding amount included in measurement of lease receivable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479773/842-30-50-5 + Details
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