Stockholders' Equity - Changes in Stockholders' Equity (Details) - USD ($) shares in Thousands, $ in Millions	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Changes in Stockholders' Equity
Beginning Balance, Treasury Shares	(3,400)
Beginning Balance	$ 21,982	$ 20,926
Consolidated net income attributable to Southern Company	485	508
Other comprehensive income (loss)	(114)	(15)
Stock issued	270	112
Stock-based compensation	60	53
Stock repurchased, at cost		(115)
Cash dividends on common stock	(497)	(478)
Contributions from noncontrolling interests	129
Distributions to noncontrolling interests	(4)
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	129
Payments to Noncontrolling Interests	4	0
Net income attributable to noncontrolling interests	1
Other	$ 1	3
Beginning Balance, Treasury Shares	(3,400)
Ending Balance	$ 22,184	$ 20,994
Number of Common shares Issued [Member]
Changes in Stockholders' Equity
Beginning Balance, Shares	915,073	908,502
Stock issued, Shares	6,572	3,094
Ending Balance, Shares	921,645	911,596
Number of Common shares Treasury [Member]
Changes in Stockholders' Equity
Beginning Balance, Treasury Shares	(3,352)	(725)
Stock repurchased, at cost, Shares		(2,599)
Other, Shares	(35)	(11)
Beginning Balance, Treasury Shares	(3,387)	(3,335)
Common Stockholders' Equity [Member]
Changes in Stockholders' Equity
Beginning Balance	$ 20,592	$ 19,949
Consolidated net income attributable to Southern Company	485	508
Other comprehensive income (loss)	(114)	(15)
Stock issued	270	112
Stock-based compensation	60	53
Stock repurchased, at cost		(115)
Cash dividends on common stock	(497)	(478)
Other	1	3
Ending Balance	20,797	20,017
Preferred And Preference Stock [Member]
Changes in Stockholders' Equity
Beginning Balance	609	756
Stock issued		0
Other	0
Ending Balance	609	756
Noncontrolling Interest [Member]
Changes in Stockholders' Equity
Beginning Balance	781	221
Contributions from noncontrolling interests	129
Distributions to noncontrolling interests	(4)
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	129
Net income attributable to noncontrolling interests	1
Ending Balance	$ 778	$ 221

Noncontrolling Interest, Increase from Contributions from Noncontrolling Interest Holders

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This element represents the amount of recognized equity-based compensation during the period, that is, the amount recognized as expense in the income statement (or as asset if compensation is capitalized). Alternate captions include the words "stock-based compensation".

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Amount of paid and unpaid common stock dividends declared with the form of settlement in cash.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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Decrease in noncontrolling interest balance from payment of dividends or other distributions by the non-wholly owned subsidiary or partially owned entity, included in the consolidation of the parent entity, to the noncontrolling interest holders.

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Decrease in noncontrolling interest (for example, but not limited to, redeeming or purchasing the interests of noncontrolling shareholders, issuance of shares (interests) by the non-wholly owned subsidiary to the parent entity for other than cash, and a buyback of shares (interest) by the non-wholly owned subsidiary from the noncontrolling interests).

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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

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Amount after tax of income (loss) attributable to other redeemable noncontrolling equity holder.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Amount of cash outflow to a noncontrolling interest. Includes, but not limited to, reduction of noncontrolling interest ownership. Excludes dividends paid to the noncontrolling interest.

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Number of shares of stock issued as of the balance sheet date, including shares that had been issued and were previously outstanding but which are now held in the treasury.

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Number of new stock issued during the period.

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Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.

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Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

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This element represents movements included in the statement of changes in stockholders' equity which are not separately disclosed or provided for elsewhere in the taxonomy.

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No definition available.

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This element represents movements in the number of shares included in the statement of changes in stockholders' equity which are not separately disclosed or provided for elsewhere in the taxonomy.

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No definition available.

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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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