Temporary Equity, Dividend Rate Percentage

No definition available.

Name:	so_TemporaryEquityDividendRatePercentage
Namespace Prefix:	so_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- 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.

+ References

No definition available.

+ Details

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

- Definition

Per share amount of par value or stated value of stock classified as temporary equity. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
-SubTopic 10
-Section S99
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=65877616&loc=d3e177068-122764

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (27)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_TemporaryEquityParOrStatedValuePerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount to be paid per share that is classified as temporary equity by entity upon redemption. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

+ References

+ Details

Name:	us-gaap_TemporaryEquityRedemptionPricePerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of securities classified as temporary equity that have been issued and are held by the entity's shareholders. Securities outstanding equals securities issued minus securities held in treasury. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(27)(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_TemporaryEquitySharesOutstanding
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	dei_LegalEntityAxis=so_AlabamaPowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=so_FourPointNineTwoPercentRedeemablePreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=so_FourPointSevenTwoPercentRedeemablePreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=so_FourPointSixFourPercentRedeemablePreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=so_FourPointSixZeroPercentRedeemablePreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=so_FourPointFiveTwoPercentRedeemablePreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=so_FourPointTwoZeroPercentRedeemablePreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=so_FivePercentClassAPreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

FINANCING - Preferred Stock Redemption (Details) - Alabama Power	12 Months Ended
	Dec. 31, 2019 $ / shares shares	Dec. 31, 2017 $ / shares shares	Oct. 02, 2022 $ / shares
4.92% Preferred Stock
Debt Instrument, Redemption [Line Items]
Temporary equity, dividend rate percentage	0.0492
Temporary equity, par value (in dollars per share)	$ 100
Shares outstanding (in shares) \| shares	80,000
Redemption Price Per Share (in dollars per share)	$ 103.23
4.72% Preferred Stock
Debt Instrument, Redemption [Line Items]
Temporary equity, dividend rate percentage	0.0472
Temporary equity, par value (in dollars per share)	$ 100
Shares outstanding (in shares) \| shares	50,000
Redemption Price Per Share (in dollars per share)	$ 102.18
4.64% Preferred Stock
Debt Instrument, Redemption [Line Items]
Temporary equity, dividend rate percentage	0.0464
Temporary equity, par value (in dollars per share)	$ 100
Shares outstanding (in shares) \| shares	60,000
Redemption Price Per Share (in dollars per share)	$ 103.14
4.60% Preferred Stock
Debt Instrument, Redemption [Line Items]
Temporary equity, dividend rate percentage	0.046
Temporary equity, par value (in dollars per share)	$ 100
Shares outstanding (in shares) \| shares	100,000
Redemption Price Per Share (in dollars per share)	$ 104.20
4.52% Preferred Stock
Debt Instrument, Redemption [Line Items]
Temporary equity, dividend rate percentage	0.0452
Temporary equity, par value (in dollars per share)	$ 100
Shares outstanding (in shares) \| shares	50,000
Redemption Price Per Share (in dollars per share)	$ 102.93
4.20% Preferred Stock
Debt Instrument, Redemption [Line Items]
Temporary equity, dividend rate percentage	0.042
Temporary equity, par value (in dollars per share)	$ 100
Shares outstanding (in shares) \| shares	135,115
Redemption Price Per Share (in dollars per share)	$ 105.00
5.00% Class A Preferred Stock
Debt Instrument, Redemption [Line Items]
Temporary equity, dividend rate percentage	0.05	0.0500
Temporary equity, par value (in dollars per share)	$ 25	$ 25
Shares outstanding (in shares) \| shares	10,000,000	10,000,000
5.00% Class A Preferred Stock \| Scenario, Forecast
Debt Instrument, Redemption [Line Items]
Redemption Price Per Share (in dollars per share)			$ 25.50