Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions		Total	Common Stock	Treasury	Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Preferred and Preference Stock of Subsidiaries	Noncontrolling Interests	[1]	Alabama Power	Alabama Power Common Stock	Alabama Power Paid-In Capital	Alabama Power Retained Earnings	Alabama Power Accumulated Other Comprehensive Income (Loss)	Georgia Power	Georgia Power Common Stock	Georgia Power Paid-In Capital	Georgia Power Retained Earnings	Georgia Power Accumulated Other Comprehensive Income (Loss)	Mississippi Power	Mississippi Power Common Stock	Mississippi Power Paid-In Capital	Mississippi Power Retained Earnings	Mississippi Power Accumulated Other Comprehensive Income (Loss)	Southern Power		Southern Power Common Stock	Southern Power Paid-In Capital		Southern Power Retained Earnings	Southern Power Accumulated Other Comprehensive Income (Loss)	Southern Power Total Common Stockholder's Equity		Southern Power Noncontrolling Interests	[2]	Southern Company Gas	Southern Company Gas Common Stock	Southern Company Gas Paid-In Capital	Southern Company Gas Retained Earnings	Southern Company Gas Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2016			991	1								31					9					1						0										0
Beginning balance at Dec. 31, 2016		$ 26,612	$ 4,952	$ (31)	$ 9,661	$ 10,356	$ (180)	$ 609	$ 1,245		$ 6,323	$ 1,222	$ 2,613	$ 2,518	$ (30)	$ 11,356	$ 398	$ 6,885	$ 4,086	$ (13)	$ 2,943	$ 38	$ 3,525	$ (616)	$ (4)	$ 5,675		$ 0	$ 3,671		$ 724	$ 35	$ 4,430		$ 1,245		$ 9,109	$ 0	$ 9,095	$ (12)	$ 26
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Consolidated net income attributable to Southern Company		842				842					848			848		1,414			1,414		(2,590)			(2,590)		1,071					1,071		1,071				243			243
Capital contributions from (to) parent company											373		373			443		443			1,004		1,004			(2)			(2)				(2)				117		117
Other comprehensive income (loss)		(9)					(9)				4				4	3				3						(10)						(10)	(10)				(5)				(5)
Stock issued (in shares)			18
Stock issued		793	$ 86		707
Stock-based compensation		105			105
Cash dividends on common stock		(2,300)				(2,300)					(714)			(714)		(1,281)			(1,281)							(317)					(317)		(317)				(443)			(443)
Other Comprehensive Income (Loss), Transfer from Service Company	[3]																									(27)						(27)	(27)
Preferred and preference stock redemptions		(609)						(609)
Contributions from noncontrolling interests		79							79																	79									79
Distributions to noncontrolling interests		122							122																	122									122
Net income attributable to noncontrolling interests		44							44																	(44)									(44)
Reclassification from redeemable noncontrolling interests		114							114																	114									114
Other		(21)		$ (5)	(4)	(13)			1		(5)			(5)		(4)			(4)		1			1		(7)			(7)				(7)				1		2		(1)
Ending balance (in shares) at Dec. 31, 2017			1,009	1								31					9					1						0										0
Ending balance at Dec. 31, 2017		25,528	$ 5,038	$ (36)	10,469	8,885	(189)	0	1,361		6,829	$ 1,222	2,986	2,647	(26)	11,931	$ 398	7,328	4,215	(10)	1,358	$ 38	4,529	(3,205)	(4)	6,498		$ 0	3,662		1,478	(2)	5,138		1,360		9,022	$ 0	9,214	(212)	20
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Consolidated net income attributable to Southern Company		2,226				2,226					930			930		793			793		235			235		187					187		187				372			372
Return of capital																										(1,650)			(1,650)				(1,650)				(400)		(400)
Capital contributions from (to) parent company											522		522			2,994		2,994			17		17			2			2				2				42		42
Other comprehensive income (loss)		26					26				4				4	3				3						14						14	14				2				2
Stock issued (in shares)			26
Stock issued		1,090	$ 126		964
Stock-based compensation		84			84
Cash dividends on common stock		(2,425)				(2,425)					(801)			(801)		(1,396)			(1,396)							(312)					(312)		(312)				(468)			(468)
Contributions from noncontrolling interests		1,372							1,372																	1,372									1,372
Distributions to noncontrolling interests		164							164																	164									164
Net income attributable to noncontrolling interests		58							58																	(59)									(59)
Sale of noncontrolling interests		1,273			(417)				1,690																	1,273	[4]		(417)	[4]			(417)	[4]	1,690	[4]
Other		(29)		$ (2)	(6)	20	40		(1)		(7)			(1)	(6)	(2)			0	2	(1)			(1)		5			3		1	(4)	6		1		0			(4)	4
Ending balance (in shares) at Dec. 31, 2018			1,035	1								31					9					1						0										0
Ending balance at Dec. 31, 2018		29,039	$ 5,164	$ (38)	11,094	8,706	(203)	0	4,316		7,477	$ 1,222	3,508	2,775	(28)	14,323	$ 398	10,322	3,612	(9)	1,609	$ 38	4,546	(2,971)	(4)	7,284		$ 0	1,600		1,352	16	2,968		4,316		8,570	$ 0	8,856	(312)	26
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Consolidated net income attributable to Southern Company		4,739				4,739					1,070			1,070		1,720			1,720		139			139		339					339		339				585			585
Return of capital																					(150)		(150)			(755)			(755)				(755)
Capital contributions from (to) parent company											1,247		1,247			640		640			53		53			64			64				64				841		841
Other comprehensive income (loss)		(118)					(118)				4				4	(42)				(42)	1				1	(42)						(42)	(42)				(19)				(19)
Issuance of equity units	[5]	(198)			(198)
Stock issued (in shares)			19
Stock issued		844	$ 93		751
Stock-based compensation		66			66
Cash dividends on common stock		(2,570)				(2,570)					(844)			(844)		(1,576)			(1,576)							(206)					(206)		(206)				(471)			(471)
Contributions from noncontrolling interests		276							276																	276									276
Distributions to noncontrolling interests		327							327																	327									(327)
Net income attributable to noncontrolling interests		(10)							(10)																	10									10
Other		18		$ (4)	21				(1)		1			0	1											(1)									(1)
Ending balance (in shares) at Dec. 31, 2019			1,054	1								31					9					1						0										0
Ending balance at Dec. 31, 2019		$ 31,759	$ 5,257	$ (42)	$ 11,734	$ 10,877	$ (321)	$ 0	$ 4,254		$ 8,955	$ 1,222	$ 4,755	$ 3,001	$ (23)	$ 15,065	$ 398	$ 10,962	$ 3,756	$ (51)	$ 1,652	$ 38	$ 4,449	$ (2,832)	$ (3)	$ 6,622		$ 0	$ 909		$ 1,485	$ (26)	$ 2,368		$ 4,254		$ 9,506	$ 0	$ 9,697	$ (198)	$ 7

[1] Excludes redeemable noncontrolling interests. See Note 7 to the financial statements under "Southern Power – Redeemable Noncontrolling Interests" for additional information.

[2] Excludes redeemable noncontrolling interests. See Note 7 to the financial statements under "Noncontrolling Interests" for additional information.

[3] In connection with Southern Power becoming a participant to the Southern Company qualified pension plan and other postretirement benefit plan, $27 million of other comprehensive income, net of tax of $9 million, was transferred from SCS.

[4] See Note 15 under "Southern Power - Sales of Renewable Facility Interests" for additional information.

[5] See Note 8 under "Equity Units" for additional information.