Disposal Group, Including Discontinued Operation, Number Of Distribution Utilities

No definition available.

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- Definition

Natural Gas Revenues

+ References

No definition available.

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

Number of Natural Gas Distribution Utilities

+ References

No definition available.

+ Details

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- Definition

Affiliated revenues from sales of energy supplied by one producer or marketer to another for eventual resale to consumers.

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No definition available.

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- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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No definition available.

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- Definition

The number of states the entity operates in as of the balance sheet date.

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No definition available.

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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.

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No definition available.

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- Details

Name:	dei_LegalEntityAxis=so_SouthernCompanyGasMember
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- Details

Name:	dei_LegalEntityAxis=so_SouthernPowerMember
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- Details

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- Details

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- Details

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Segment and Related Information - Narrative (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($) utility state	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) utility state segment	Jun. 30, 2017 USD ($)	Aug. 07, 2018 utility state
Segment Reporting Information [Line Items]
Number of reportable segments \| segment			4
Number of states in which entity operates \| state	4		4
Natural gas revenues	$ 706	$ 684	$ 2,314	$ 2,214
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Number of reportable segments \| segment			4
Number of states in which entity operates \| state	7		7
Number of natural gas distribution utilities \| utility	7		7
Natural gas revenues	$ 710	684	$ 2,341	2,205
SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Wholesale revenues, affiliates	109	90	192	190
Traditional Electric Operating Companies \| SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Natural gas revenues	8	10	8	10
Southern Company \| SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Natural gas revenues	$ 22	$ 33	$ 58	$ 56
Subsequent Event \| SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Number of states in which entity operates \| state					4
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Subsequent Event \| SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Number of natural gas distribution utilities disposed \| utility					3