Condensed Consolidated Statements of Cash Flows (Unaudited) - GAS (Parenthetical) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024
Net cash paid for capitalized interest	$ 97	$ 76
SOUTHERN Co GAS
Net cash paid for capitalized interest	$ 12	$ 16

Amount of cash paid for interest capitalized, classified as investing activity.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 13
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-13

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482913/230-10-50-2

Name:	us-gaap_InterestPaidCapitalized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration