Condensed Consolidated Statements of Cash Flows (Unaudited) (Parenthetical) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Interest capitalized	$ 68	$ 61
ALABAMA POWER CO
Interest capitalized	11	11
GEORGIA POWER CO
Interest capitalized	47	34
SOUTHERN POWER CO
Interest capitalized	5	10
SOUTHERN Co GAS
Interest capitalized	$ 6	$ 5

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

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3213-108585

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=123431023&loc=d3e4297-108586

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration