Stockholders' Equity - Changes in Stockholders' Equity (Details) - USD ($) shares in Thousands, $ in Millions	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Changes in Stockholders' Equity
Beginning balance, treasury shares (in shares)	(800)
Beginning balance	$ 26,612	$ 21,982
Consolidated net income attributable to Southern Company	658	489
Other comprehensive income (loss)	(9)	(114)
Stock issued	186	270
Stock-based compensation	57	57
Cash dividends on common stock	(556)	(497)
Contributions from noncontrolling interests	71	129
Distributions to noncontrolling interests	(18)	(4)
Purchase of membership interests from noncontrolling interests		(129)
Net income attributable to noncontrolling interests	(4)	1
Other	$ (1)	0
Beginning balance, treasury shares (in shares)	(900)
Ending balance	$ 26,996	$ 22,184
Number of Common shares Issued [Member]
Changes in Stockholders' Equity
Beginning balance (in shares)	991,213	915,073
Stock issued (in shares)	4,240	6,572
Ending balance (in shares)	995,453	921,645
Number of Common shares Treasury [Member]
Changes in Stockholders' Equity
Beginning balance, treasury shares (in shares)	(819)	(3,352)
Stock issued (in shares)	0
Other (in shares)	(35)	(35)
Beginning balance, treasury shares (in shares)	(854)	(3,387)
Common Stockholders' Equity
Changes in Stockholders' Equity
Beginning balance	$ 24,758	$ 20,592
Consolidated net income attributable to Southern Company	658	489
Other comprehensive income (loss)	(9)	(114)
Stock issued	186	270
Stock-based compensation	57	57
Cash dividends on common stock	(556)	(497)
Other	0
Ending balance	25,094	20,797
Preferred and Preference Stock of Subsidiaries
Changes in Stockholders' Equity
Beginning balance	609	609
Ending balance	609	609
Noncontrolling Interest [Member]
Changes in Stockholders' Equity
Beginning balance	1,245	781
Contributions from noncontrolling interests	71	129
Distributions to noncontrolling interests	(18)	(4)
Purchase of membership interests from noncontrolling interests		(129)
Net income attributable to noncontrolling interests	(4)	1
Other	(1)
Ending balance	1,293	$ 778
SunPower Corp. [Member] \| Noncontrolling Interest [Member]
Changes in Stockholders' Equity
Ending balance	$ 114

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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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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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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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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Number of increase (decrease) in shares of stock classified as other.

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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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