Summary of Significant Accounting Policies - Regulatory Assets and Liabilities (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended		48 Months Ended
	Jul. 31, 2016	Dec. 31, 2019	Dec. 31, 2017	Dec. 31, 2017	Jan. 11, 2018	Dec. 31, 2016	Aug. 29, 2016
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ (1,894)	$ (1,894)		$ 5,866
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Accumulated deferred income taxes			6,842	6,842		14,092
Other cost of removal obligations
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(2,684)	(2,684)		(2,774)
Deferred income tax credits
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(7,261)	(7,261)		(219)
Over recovered regulatory clause revenues
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(155)	(155)		(203)
Property damage reserves-liability
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(135)	(135)		(177)
Other regulatory liabilities
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(266)	(266)		(120)
Retiree Benefit Plans
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			3,931	3,931		3,959
AROs
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			1,133	1,133		1,080
Other regulatory assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			511	511		487
Loss on reacquired debt
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			223	223		243
Environmental remediation-asset
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			511	511		491
Under recovered regulatory clause revenues
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			317	317		273
Property damage reserves-asset
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			333	333		206
Regulatory assets associated with the Kemper County energy facility
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			88	88		201
Vacation pay
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 183	183		182
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			1 year
Long-term debt fair value adjustment
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 138	138		155
Deferred PPA charges
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			119	119		141
Remaining net book value of retired assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			306	306		351
Deferred Income Tax Charge
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 814	814		1,590
Maximum
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Life of new issue			50 years
Power purchase agreement period			6 years
Maximum | Other regulatory liabilities
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory liability, amortization period			20 years
Maximum | Retiree Benefit Plans
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			15 years
Maximum | Other regulatory assets
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			50 years
Maximum | Asset Group 1
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			10 years
Maximum | Remaining net book value of retired assets
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			48 years
Maximum | Deferred Income Tax Charge
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			80 years
ALABAMA POWER CO
Schedule of Regulatory Assets and Liabilities [Line Items]
Fuel hedging assets and liabilities, amortization period			3 years 6 months
Total assets (liabilities), net			$ (1,088)	(1,088)		1,047
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Medicare drug subsidy obligation related to subsidiary			13	13		16
ALABAMA POWER CO | Other cost of removal obligations
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(609)	(609)		(684)
ALABAMA POWER CO | Deferred income tax credits
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(2,082)	(2,082)		(65)
ALABAMA POWER CO | Over recovered regulatory clause revenues
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			53	53		76
ALABAMA POWER CO | Other regulatory liabilities
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(7)	(7)		(23)
ALABAMA POWER CO | AROs
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net						12
ALABAMA POWER CO | Natural disaster reserve
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(38)	(38)		(69)
ALABAMA POWER CO | Retiree Benefit Plans
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			946	946		947
ALABAMA POWER CO | AROs
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(33)	(33)
ALABAMA POWER CO | Other regulatory assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			51	51		50
ALABAMA POWER CO | Loss on reacquired debt
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			62	62		68
ALABAMA POWER CO | Under recovered regulatory clause revenues
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			142	142		0
ALABAMA POWER CO | Vacation pay
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			70	70		69
ALABAMA POWER CO | Nuclear outage
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			56	56		70
ALABAMA POWER CO | Fuel-hedging-asset
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			7	7		1
ALABAMA POWER CO | Remaining net book value of retired assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 54	54		69
ALABAMA POWER CO | Remaining net book value of retired assets
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			11 years
ALABAMA POWER CO | Deferred Income Tax Charge
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 240	240		526
ALABAMA POWER CO | Maximum
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Life of new issue			50 years
ALABAMA POWER CO | Maximum | Retiree Benefit Plans
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			15 years
ALABAMA POWER CO | Maximum | Deferred income tax charges
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			15 years
ALABAMA POWER CO | Maximum | Nuclear outage
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			10 years
ALABAMA POWER CO | Maximum | Deferred Income Tax Charge
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			50 years
GEORGIA POWER CO
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 232	232		3,506
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Refueling cycles maximum period			24 months
GEORGIA POWER CO | Other cost of removal obligations
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 40	40		3
GEORGIA POWER CO | Deferred income tax credits
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(3,248)	(3,248)		(121)
GEORGIA POWER CO | Other regulatory liabilities
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(191)	(191)		(39)
GEORGIA POWER CO | Retiree Benefit Plans
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 1,313	1,313		1,348
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			14 years
GEORGIA POWER CO | Deferred income tax charges
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 21	21
GEORGIA POWER CO | AROs
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			945	945		893
GEORGIA POWER CO | Other regulatory assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 119	119		97
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			24 months
Amortization of regulatory assets			$ 54
GEORGIA POWER CO | Loss on reacquired debt
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			127	127		137
GEORGIA POWER CO | Vacation pay
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 91	91		91
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			1 year
GEORGIA POWER CO | Canceled Construction Projects
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 36	36		44
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			9 years
GEORGIA POWER CO | Remaining net book value of retired assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 146	146		166
GEORGIA POWER CO | Obsolete Inventories of Retired Units
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			31	31
GEORGIA POWER CO | Storm damage reserves
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			333	333		206
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Amortization of regulatory assets				319
GEORGIA POWER CO | Deferred Income Tax Charge
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			521	521		681
Tax Cuts and Jobs Act of 2017, Deferred Tax Assets Related to CWIP			145	145
Tax Cuts and Jobs Act of 2017, Deferred Tax Liabilities			626	626
GEORGIA POWER CO | Plant Mitchell Unit 3
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Net book value of planned units retirements			$ 10	10
GEORGIA POWER CO | Maximum
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Life of new issue			35 years
GEORGIA POWER CO | Maximum | Deferred Income Tax Charge, AROs, Cost Of Removal Obligations, Deferred Income Tax Credits
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			65 years
GEORGIA POWER CO | Maximum | Remaining net book value of retired assets
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			10 years
GEORGIA POWER CO | Scenario, Forecast | Remaining net book value of retired assets
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Amortization of regulatory assets		$ 4
GULF POWER CO
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ (105)	(105)		320
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory asset							$ 63
Life of new issue			40 years
GULF POWER CO | Over Under Recovered Regulatory Clause Revenues
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			1 year
GULF POWER CO | Deferred Income Tax Charge
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ (458)	(458)		(2)
GULF POWER CO | Other cost of removal obligations
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(221)	(221)		(278)
GULF POWER CO | Deferred income tax credits
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Accumulated deferred income taxes			71	71
GULF POWER CO | Over recovered regulatory clause revenues
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(11)	(11)		(23)
GULF POWER CO | Property damage reserves-liability
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(40)	(40)		(40)
GULF POWER CO | AROs
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net						7
GULF POWER CO | Retiree Benefit Plans
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			166	166		160
GULF POWER CO | AROs
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			13	13
GULF POWER CO | Other regulatory assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			36	36		18
GULF POWER CO | Loss on reacquired debt
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			17	17		18
GULF POWER CO | Environmental remediation-asset
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			52	52		44
GULF POWER CO | Deferred Return On Transmission Upgrades
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 25	25		25
GULF POWER CO | Vacation pay
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			1 year
GULF POWER CO | Deferred PPA charges
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 119	119		141
GULF POWER CO | Ash Pond Closure
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 80	80		75
GULF POWER CO | Fuel Hedging Assets and Liabilities
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			4 years
GULF POWER CO | Fuel-hedging-asset
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 21	21		24
GULF POWER CO | Remaining net book value of retired assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			65	65		66
GULF POWER CO | Regulatory asset, offset to other cost of removal
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			0	0		29
GULF POWER CO | Deferred Income Tax Charge
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 31	31		56
GULF POWER CO | Maximum | Deferred income tax credits
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			65 years
GULF POWER CO | Maximum | Retiree Benefit Plans
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			14 years
GULF POWER CO | Maximum | Deferred PPA charges
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			6 years
GULF POWER CO | Maximum | Deferred Income Tax Charge, AROs, Cost Of Removal Obligations, Deferred Income Tax Credits
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			65 years
MISSISSIPPI POWER CO
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ (42)	(42)		737
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period	5 years
MISSISSIPPI POWER CO | Deferred Credits Related To Income Taxes [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(377)	(377)		(9)
Deferred tax assets from tax reform			375	375
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Tax Cuts and Jobs Act of 2017, Protected Deferred Tax Assets			273	273
Tax Cuts and Jobs Act of 2017, Unprotected Deferred Tax Assets			102	102
MISSISSIPPI POWER CO | Other cost of removal obligations
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(178)	(178)		(170)
MISSISSIPPI POWER CO | Property damage reserves-liability
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(57)	(57)		(68)
MISSISSIPPI POWER CO | Other regulatory liabilities
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			0	0		(1)
MISSISSIPPI POWER CO | Kemper IGCC
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			88	88		194
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory asset			114	114
Regulatory assets, noncurrent			$ 26	26
MISSISSIPPI POWER CO | Retiree Benefit Plans
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			15 years
MISSISSIPPI POWER CO | AROs
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 95	95		83
MISSISSIPPI POWER CO | Other regulatory assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 28	28		28
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			50 years
MISSISSIPPI POWER CO | Remaining net book value of retired assets
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			48 years
MISSISSIPPI POWER CO | Remaining net book value of retired assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 44	44		53
MISSISSIPPI POWER CO | Property Tax
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 43	43		37
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			12 months
MISSISSIPPI POWER CO | Deferred Income Tax Charge
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 36	36		362
MISSISSIPPI POWER CO | Retiree Benefit Plans - Regulatory Assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			174	174		173
MISSISSIPPI POWER CO | ECO Carryforward [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			26	26		22
MISSISSIPPI POWER CO | Kemper IGCC
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory asset			114	114
MISSISSIPPI POWER CO | Kemper IGCC | Deferred Credits Related To Income Taxes [Member]
Schedule of Regulatory Assets and Liabilities [Line Items]
Deferred tax assets from tax reform			$ 129	129
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			8 years
Tax Cuts and Jobs Act of 2017, Unprotected Deferred Tax Assets			$ 54	54
MISSISSIPPI POWER CO | Plant Daniel Units 3 and 4
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			10 years
MISSISSIPPI POWER CO | Plant Daniel Units 3 and 4 | Plant Daniel Units 3 and 4
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 36	36		33
MISSISSIPPI POWER CO | Amortization Period One | Fuel Hedging Assets and Liabilities
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			8 years
MISSISSIPPI POWER CO | Amortization Period Two | Fuel Hedging Assets and Liabilities
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			6 years
SOUTHERN Co GAS
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ (1,879)	(1,879)		(715)
SOUTHERN Co GAS | Environmental Remediation
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			410	410		411
SOUTHERN Co GAS | Other cost of removal obligations
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(1,646)	(1,646)		(1,616)
SOUTHERN Co GAS | Deferred income tax credits
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(1,063)	(1,063)		(22)
SOUTHERN Co GAS | Over recovered regulatory clause revenues
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(144)	(144)		(104)
SOUTHERN Co GAS | Other regulatory liabilities
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			(21)	(21)		(39)
SOUTHERN Co GAS | Other regulatory assets
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 79	79		58
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			12 months
SOUTHERN Co GAS | Under recovered regulatory clause revenues
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 98	98		118
SOUTHERN Co GAS | Vacation pay
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			1 year
SOUTHERN Co GAS | Long-term debt fair value adjustment
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 270	270		325
SOUTHERN Co GAS | Environmental Remediation
Schedule of Regulatory Assets and Liabilities [Line Items]
Total assets (liabilities), net			$ 138	138		$ 154
SOUTHERN Co GAS | Over Under Recovered Regulatory Clause Revenues
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			8 years
SOUTHERN Co GAS | Maximum | Retiree Benefit Plans
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			15 years
SOUTHERN Co GAS | Maximum | Other regulatory assets
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			10 years
SOUTHERN Co GAS | Maximum | Long-term debt fair value adjustment
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			21 years
SOUTHERN Co GAS | Maximum | Financial Instrument Hedging
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			2 years
SOUTHERN Co GAS | Maximum | Other regulatory liabilities
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			20 years
SOUTHERN Co GAS | Maximum | Deferred Income Tax Charges and Other Cost of Removal Obligations
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			80 years
SOUTHERN Co GAS | Minimum | Other regulatory liabilities
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Regulatory amortization period			4 years
Subsequent Event | GEORGIA POWER CO | Other regulatory liabilities
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Customer Refund Liability, Noncurrent					$ 188
Retail [Member] | MISSISSIPPI POWER CO | Kemper IGCC | Deferred Credits Related To Income Taxes [Member]
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Tax Cuts and Jobs Act of 2017, Unprotected Deferred Tax Assets			$ 38	38
Wholesale [Member] | MISSISSIPPI POWER CO | Kemper IGCC | Deferred Credits Related To Income Taxes [Member]
Schedule of Regulatory Assets and Liabilities - Other Information [Abstract]
Tax Cuts and Jobs Act of 2017, Unprotected Deferred Tax Assets			$ 16	$ 16