Consolidated Statements of Capitalization (Parenthetical) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Common stock, par value (in dollars per share)	$ 5	$ 5
Common stock, shares authorized (in shares)	1,500,000,000	1,500,000,000
Common stock, shares issued (in shares)	1,100,000,000	1,000,000,000
Treasury shares (in shares)	1,000,000	1,000,000
Redeemable Preferred Stock, $100 par or stated value
Preferred stock, par value (in dollars per share)	$ 100	$ 100
Redeemable cumulative preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Redeemable cumulative preferred stock, shares outstanding (in shares)	475,115	475,115
Redeemable Preferred Stock, $1 par value
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, dividend rate	5.00%	5.00%
Redeemable cumulative preferred stock, shares authorized (in shares)	28,000,000	28,000,000
Redeemable cumulative preferred stock, shares outstanding (in shares)	10,000,000	10,000,000
Redeemable Preferred Stock
Annual dividend requirement	$ 15,000,000	$ 15,000,000
Alabama Power
Common stock, par value (in dollars per share)	$ 40	$ 40
Common stock, shares authorized (in shares)	40,000,000	40,000,000
Common stock, shares outstanding (in shares)	30,537,500	30,537,500
Alabama Power \| Cumulative preferred stock
Annual dividend requirement	$ 15,000,000	$ 15,000,000
Alabama Power \| Redeemable Preferred Stock, $100 par or stated value \| Cumulative preferred stock
Preferred stock, par value (in dollars per share)	$ 100	$ 100
Redeemable cumulative preferred stock, shares authorized (in shares)	3,850,000	3,850,000
Redeemable cumulative preferred stock, shares outstanding (in shares)	475,115	475,115
Alabama Power \| Redeemable Preferred Stock, $1 par value \| Cumulative preferred stock
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, dividend rate	5.00%	5.00%
Redeemable cumulative preferred stock, shares authorized (in shares)	27,500,000	27,500,000
Redeemable cumulative preferred stock, shares outstanding (in shares)	10,000,000	10,000,000
Alabama Power \| Redeemable Preferred Stock, $25 stated value \| Cumulative preferred stock
Preferred stock, par value (in dollars per share)	$ 25	$ 25
Georgia Power
Common stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, shares outstanding (in shares)	9,261,500	9,261,500
Mississippi Power
Common stock, shares authorized (in shares)	1,130,000	1,130,000
Common stock, shares outstanding (in shares)	1,121,000	1,121,000
Southern Company Gas
Common stock, par value (in dollars per share)	$ 0.01	$ 10,000.00
Common stock, shares authorized (in shares)	100,000,000	100
Common stock, shares outstanding (in shares)	100	100
Minimum \| Redeemable Preferred Stock, $100 par or stated value \| Cumulative preferred stock
Preferred stock, dividend rate	4.20%
Minimum \| Alabama Power \| Redeemable Preferred Stock, $100 par or stated value \| Cumulative preferred stock
Preferred stock, dividend rate	4.20%	4.20%
Maximum \| Redeemable Preferred Stock, $100 par or stated value \| Cumulative preferred stock
Preferred stock, dividend rate	4.92%
Maximum \| Alabama Power \| Redeemable Preferred Stock, $100 par or stated value \| Cumulative preferred stock
Preferred stock, dividend rate	4.92%	4.92%

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Face amount or stated value per share of common stock.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

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The maximum number of securities classified as temporary equity that are permitted to be issued by an entity's charter and bylaws. 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.

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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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