Consolidated Entities and Equity Method Investments - Schedule of Equity Method Investments (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2022	Dec. 31, 2021
Schedule of Equity Method Investments [Line Items]
Investment Balance	$ 1,293	$ 1,282
SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Investment Balance	1,178	1,173
SOUTHERN Co GAS \| SNG
Schedule of Equity Method Investments [Line Items]
Investment Balance	1,138	1,129
SOUTHERN Co GAS \| Other
Schedule of Equity Method Investments [Line Items]
Investment Balance	40	$ 44
SOUTHERN Co GAS \| PennEast Pipeline
Schedule of Equity Method Investments [Line Items]
Distribution	$ 4

Amount of distribution received from equity method investee for return on investment, classified as operating activities. Excludes distribution for return of investment, classified as investing activities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(10))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(12))
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 21D
-URI http://asc.fasb.org/extlink&oid=123570139&loc=SL94080555-108585

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