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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-3

Name:	us-gaap_TaxCreditCarryforwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Income and Other Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Southern Power
Tax Credit Carryforward [Line Items]
Percentage reduction in tax basis of assets	50.00%
Southern Company Gas
Tax Credit Carryforward [Line Items]
Excise taxes collected	$ 136	$ 115	$ 133
Included In Operating Expenses \| Southern Company Gas
Tax Credit Carryforward [Line Items]
Excise taxes collected	$ 132	$ 112	$ 129