Financing - Textual (Details)			1 Months Ended											2 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended
	Oct. 26, 2016	Feb. 20, 2014 USD ($)	Dec. 31, 2017 USD ($) leased_asset_units series $ / shares shares	Nov. 30, 2017 USD ($) shares	Oct. 31, 2017 USD ($) shares	Sep. 30, 2017 USD ($) $ / shares shares	Aug. 31, 2017 USD ($)	Jul. 31, 2017 USD ($)	Jun. 30, 2017 USD ($) agreement shares	May 31, 2017 USD ($)	Feb. 28, 2017 USD ($)	Jan. 31, 2017 USD ($) shares	Sep. 30, 2013	Feb. 20, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) leased_asset_units series $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($)	Dec. 31, 2012 USD ($)	Jan. 04, 2018 USD ($)	Nov. 01, 2017 USD ($)	Oct. 04, 2017 USD ($)	Sep. 29, 2017 USD ($)	Aug. 10, 2017 USD ($)	Apr. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 08, 2016 USD ($)	Aug. 31, 2015	Dec. 31, 2014 USD ($)	Dec. 31, 2013
Debt Instrument [Line Items]
Line of Credit Terminated										$ 1,000,000,000
Long-term Debt and Capital Lease Obligations, Current			$ 3,892,000,000													$ 2,587,000,000	$ 3,892,000,000	$ 2,587,000,000
2022			2,016,000,000													1,378,000,000	2,016,000,000	1,378,000,000
Redeemable preferred stock			324,000,000													118,000,000	324,000,000	118,000,000
Financing (Textual) [Abstract]
Proceeds from issuance of junior subordinated notes			206,000,000													206,000,000	206,000,000	206,000,000
Other long-term debt			10,987,000,000													9,404,000,000	10,987,000,000	9,404,000,000
Senior notes, current			2,354,000,000													1,995,000,000	2,354,000,000	1,995,000,000
Other Long-term Debt			1,420,000,000													485,000,000	1,420,000,000	485,000,000
Long term debt and capital lease obligations, maturities in 2018			3,900,000,000														3,900,000,000
Long term debt and capital lease obligations, maturities in 2019			3,200,000,000														3,200,000,000
Long term debt and capital lease obligations, maturities in 2020			3,200,000,000														3,200,000,000
Long Term Debt and Capital Lease Obligation Maturities Repayments in 2021			3,100,000,000														3,100,000,000
Long term debt and capital lease obligations, maturities in 2022			2,200,000,000														2,200,000,000
2018			2,402,000,000													2,403,000,000	2,402,000,000	2,403,000,000
2019			3,074,000,000													3,076,000,000	3,074,000,000	3,076,000,000
Long-term debt, maturities, repayments of principal after year five			$ 22,142,000,000													20,369,000,000	$ 22,142,000,000	20,369,000,000
Ratio of indebtedness to capitalization, debt covenant, required			70.00%														70.00%														65.00%
Senior notes			$ 35,100,000,000													33,000,000,000	$ 35,100,000,000	33,000,000,000
Capitalized lease obligations			204,000,000													136,000,000	204,000,000	136,000,000
Accumulated depreciation PPE			31,457,000,000													29,852,000,000	31,457,000,000	29,852,000,000
Unused credit with banks			8,094,000,000														8,094,000,000
Amount of variable rate pollution control revenue bonds outstanding requiring liquidity support			1,500,000,000													1,900,000,000	1,500,000,000	1,900,000,000
Short term borrowings excluding other energy service contracts			$ 2,439,000,000													$ 2,032,000,000	2,439,000,000	$ 2,032,000,000
Remarketed pollution control bonds																	$ 714,000,000
Common stock, shares issued | shares			1,000,000,000													991,000,000	1,000,000,000	991,000,000
Common stock																	$ 793,000,000	$ 3,758,000,000	$ 256,000,000
Short-term debt			$ 2,439,000,000													$ 2,241,000,000	$ 2,439,000,000	2,241,000,000
Commitment fee percentage (less than 1/4 of 1%)																	0.25%
Line of credit facility, maximum borrowing capacity			8,145,000,000														$ 8,145,000,000
2020			2,273,000,000													1,326,000,000	2,273,000,000	1,326,000,000
Capitalized leases			31,000,000													32,000,000	31,000,000	32,000,000
Unamortized debt issuance expense			(3,000,000)													(1,000,000)	(3,000,000)	(1,000,000)
2021			2,643,000,000													2,655,000,000	2,643,000,000	2,655,000,000
Expires, 2018			195,000,000														195,000,000
Line Of Credit Expire Year Three			725,000,000														725,000,000
Assets			111,005,000,000													109,697,000,000	111,005,000,000	109,697,000,000	78,318,000,000
Stock Redeemed or Called During Period, Value																	609,000,000		150,000,000
Subsequent Event
Financing (Textual) [Abstract]
Remarketed pollution control bonds														$ 50,000,000
Building
Financing (Textual) [Abstract]
Capital leased assets, gross			216,000,000													61,000,000	216,000,000	61,000,000
Junior subordinated notes (5.00% to 6.25%) due 2057 to 2077
Financing (Textual) [Abstract]
Junior subordinated notes			3,570,000,000													2,350,000,000	3,570,000,000	2,350,000,000
Trust Preferred Securities Subject to Mandatory Redemption
Financing (Textual) [Abstract]
Preferred securities, outstanding			200,000,000													200,000,000	200,000,000	200,000,000
Senior Notes
Financing (Textual) [Abstract]
Debt instrument, face amount			300,000,000														300,000,000
Floating rate Promissory Note Due July 2018 | Subsequent Event
Financing (Textual) [Abstract]
Debt instrument, face amount																					$ 100,000,000
Subsidiaries
Financing (Textual) [Abstract]
Capitalized lease obligations			$ 177,000,000													29,000,000	$ 177,000,000	29,000,000
Subsidiaries | Capital Lease Obligations | Minimum
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation			1.50%														1.50%
Subsidiaries | Capital Lease Obligations | Maximum
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation			4.70%														4.70%
Parent Company
Financing (Textual) [Abstract]
Bank loans			$ 450,000,000													400,000,000	$ 450,000,000	400,000,000
Ratio of indebtedness to capitalization, debt covenant, required			70.00%														70.00%
Senior notes			$ 10,200,000,000													10,300,000,000	$ 10,200,000,000	10,300,000,000
Unused credit with banks			1,999,000,000														1,999,000,000
Line of credit facility, maximum borrowing capacity			2,000,000,000														2,000,000,000
Expires, 2018			0														0
Line Of Credit Expire Year Three			0														0
Parent Company | Notes Payable to Banks [Member] | Floating Rate Bank Term Loan Agreement [Member]
Financing (Textual) [Abstract]
Number of Loan Agreements | agreement									2
Parent Company | Notes Payable to Banks [Member] | Floating Rate Bank Term Loan Agreement 4 [Member]
Financing (Textual) [Abstract]
Debt instrument, face amount									$ 100,000,000						$ 100,000,000
Parent Company | Junior Subordinated Debt | Senior Notes Due 2076
Financing (Textual) [Abstract]
Debt instrument, face amount																												$ 500,000,000
Fixed stated interest rate of debt obligation																												5.325%
Parent Company | Junior Subordinated Debt | Junior Subordinated Notes Due Two Thousand Seventy Seven [Member]
Financing (Textual) [Abstract]
Debt instrument, face amount				$ 450,000,000
Fixed stated interest rate of debt obligation				5.25%
Parent Company | Line of Credit | Uncommitted Bank Credit Arrangement [Member]
Financing (Textual) [Abstract]
Proceeds from Issuance of Debt							$ 250,000,000
Debt Instrument, Payable by Demand from Bank, Term							30 days
ALABAMA POWER CO
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations, Current			0													561,000,000	0	561,000,000
2022			$ 750,000,000													200,000,000	$ 750,000,000	200,000,000
Ownership percentage, equity method investment			50.00%														50.00%
Redeemable preferred stock			$ 291,000,000													85,000,000	$ 291,000,000	85,000,000
Senior notes and pollution control revenue bonds, current			0													561,000,000	0	561,000,000
Financing (Textual) [Abstract]
Proceeds from issuance of junior subordinated notes			206,000,000													206,000,000	206,000,000	206,000,000
Other long-term debt			1,060,000,000													1,096,000,000	1,060,000,000	1,096,000,000
2019			200,000,000													200,000,000	200,000,000	200,000,000
Long-term debt, maturities, repayments of principal after year five			4,975,000,000													4,425,000,000	4,975,000,000	4,425,000,000
Bank loans			$ 45,000,000													45,000,000	$ 45,000,000	45,000,000
Ratio of indebtedness to capitalization, debt covenant, required			65.00%														65.00%
Percent ownership			14.00%														14.00%
Pollution control revenue bonds, outstanding			$ 1,060,000,000													1,100,000,000	$ 1,060,000,000	1,100,000,000
Repayments of senior debt																	525,000,000	200,000,000	650,000,000
Capitalized lease obligations			4,000,000													4,000,000	4,000,000	4,000,000
Accumulated depreciation PPE			9,563,000,000													9,112,000,000	9,563,000,000	9,112,000,000
Unused credit with banks			1,335,000,000														1,335,000,000
Amount of variable rate pollution control revenue bonds outstanding requiring liquidity support			854,000,000														854,000,000
Pollution control revenue bonds required to be remarketed			120,000,000														120,000,000
Short-term debt outstanding, regulatory approved maximum			2,000,000,000														2,000,000,000
Short-term debt			3,000,000													0	$ 3,000,000	0
Commitment fee percentage (less than 1/4 of 1%)																	0.10%
Line of credit facility, maximum borrowing capacity			1,335,000,000														$ 1,335,000,000
2020			250,000,000													250,000,000	250,000,000	250,000,000
2021			220,000,000													220,000,000	220,000,000	220,000,000
Capital contributions from parent company																	361,000,000	260,000,000	22,000,000
Expires, 2018			35,000,000														35,000,000
Line Of Credit Expire Year Three			500,000,000			$ 500,000,000											500,000,000
Assets			23,864,000,000													22,516,000,000	23,864,000,000	22,516,000,000
ALABAMA POWER CO | Trust Preferred Securities Subject to Mandatory Redemption
Financing (Textual) [Abstract]
Preferred securities, outstanding			200,000,000													200,000,000	200,000,000	200,000,000
ALABAMA POWER CO | Senior Notes And Pollution Control Bond
Debt Instrument [Line Items]
2022			750,000,000														750,000,000
Financing (Textual) [Abstract]
2018			0														0
2019			200,000,000														200,000,000
2020			250,000,000														250,000,000
2021			310,000,000														310,000,000
ALABAMA POWER CO | Bank Loans [Member]
Financing (Textual) [Abstract]
Debt instrument, face amount			45,000,000													$ 45,000,000	45,000,000	$ 45,000,000
ALABAMA POWER CO | Capital Lease Obligations
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																6.90%		6.90%
ALABAMA POWER CO | Senior Notes | Series 2016A
Financing (Textual) [Abstract]
Debt instrument, face amount																											$ 550,000,000
Fixed stated interest rate of debt obligation																											2.45%
ALABAMA POWER CO | Senior Notes | Series 2017B
Financing (Textual) [Abstract]
Debt instrument, face amount				$ 550,000,000
Fixed stated interest rate of debt obligation				3.70%
ALABAMA POWER CO | Unsecured Debt
Financing (Textual) [Abstract]
Senior notes			6,400,000,000													$ 5,800,000,000	6,400,000,000	$ 5,800,000,000
ALABAMA POWER CO | Line of Credit | Alabama Power Company Project
Financing (Textual) [Abstract]
Repayments of debt							$ 36,100,000
GEORGIA POWER CO
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations, Current			857,000,000													460,000,000	857,000,000	460,000,000
2022			400,000,000													400,000,000	400,000,000	400,000,000
Financing (Textual) [Abstract]
Other long-term debt			4,716,000,000													4,445,000,000	4,716,000,000	4,445,000,000
Senior notes, current			750,000,000													450,000,000	750,000,000	450,000,000
Other Long-term Debt			100,000,000													0	100,000,000	0
Long term debt and capital lease obligations, maturities in 2017			861,000,000														861,000,000
Long term debt and capital lease obligations, maturities in 2019			513,000,000														513,000,000
Long term debt and capital lease obligations, maturities in 2020			1,000,000,000														1,000,000,000
Long Term Debt and Capital Lease Obligation Maturities Repayments in 2021			375,000,000														375,000,000
Long term debt and capital lease obligations, maturities in 2022			518,000,000														518,000,000
2018			747,000,000													748,000,000	747,000,000	748,000,000
2019			499,000,000													500,000,000	499,000,000	500,000,000
Long-term debt, maturities, repayments of principal after year five			4,175,000,000													3,775,000,000	4,175,000,000	3,775,000,000
Bank loans			$ 250,000,000														$ 250,000,000
Ratio of indebtedness to capitalization, debt covenant, required			65.00%														65.00%
Percent of eligible project costs to be reimbursed		70.00%
Eligible project costs to be reimbursed		$ 3,460,000,000
Debt Instrument, basis spread on variable rate		0.375%
Senior notes			$ 7,100,000,000													6,200,000,000	$ 7,100,000,000	6,200,000,000
Amortization period for line of credit facility		5 years
Pollution control revenue bonds, outstanding			$ 1,800,000,000													1,800,000,000	$ 1,800,000,000	1,800,000,000
Fixed stated interest rate of debt obligation			2.00%														2.00%
Repayments of senior debt																	$ 450,000,000	700,000,000	1,175,000,000
Capitalized lease obligations			$ 154,000,000													169,000,000	154,000,000	169,000,000
Accumulated depreciation PPE			11,704,000,000													11,317,000,000	11,704,000,000	11,317,000,000
Unused credit with banks			1,732,000,000														1,732,000,000
Amount of variable rate pollution control revenue bonds outstanding requiring liquidity support			550,000,000													868,000,000	550,000,000	868,000,000
Pollution control revenue bonds required to be remarketed			469,000,000														469,000,000
Short-term debt			150,000,000													391,000,000	$ 150,000,000	391,000,000
Commitment fee percentage (less than 1/4 of 1%)																	0.25%
Line of credit facility, maximum borrowing capacity			1,750,000,000														$ 1,750,000,000
2020			950,000,000													0	950,000,000	0
Capitalized leases			11,000,000													10,000,000	11,000,000	10,000,000
Unamortized debt issuance expense			(1,000,000)													0	(1,000,000)	0
2021			325,000,000													325,000,000	325,000,000	325,000,000
Capital contributions from parent company																	431,000,000	594,000,000	62,000,000
Expires, 2018			0														0
Line Of Credit Expire Year Three			0														0
Assets			$ 36,779,000,000													34,835,000,000	$ 36,779,000,000	34,835,000,000
Preference stock, shares outstanding | shares			0														0
GEORGIA POWER CO | Corporate, Non-Segment
Financing (Textual) [Abstract]
Capital leased assets, gross			$ 61,000,000														$ 61,000,000
Capitalized lease obligations																61,000,000		61,000,000
Accumulated depreciation PPE			39,000,000													33,000,000	39,000,000	33,000,000
GEORGIA POWER CO | Building
Financing (Textual) [Abstract]
Capitalized lease obligations			22,000,000													28,000,000	22,000,000	28,000,000
GEORGIA POWER CO | Municipal Bonds [Member] | Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Fifth Series 1995 [Member]
Financing (Textual) [Abstract]
Debt instrument, face amount																										$ 27,000,000
GEORGIA POWER CO | Municipal Bonds [Member] | Development Authority of Bartow County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Bowen Project), First Series 1997 [Member]
Financing (Textual) [Abstract]
Debt instrument, face amount							38,000,000
GEORGIA POWER CO | Notes Payable to Banks [Member] | Floating Rate Bank Term Loan Agreement [Member]
Financing (Textual) [Abstract]
Number of Loan Agreements | agreement									3
Debt Instrument, Payable by Demand from Bank, Term									30 days
GEORGIA POWER CO | Notes Payable to Banks [Member] | Bank Term Loans
Financing (Textual) [Abstract]
Long-term debt			$ 250,000,000													$ 0	$ 250,000,000	$ 0
GEORGIA POWER CO | Notes Payable to Banks [Member] | Floating Rate Bank Term Loan Agreement 1 [Member]
Financing (Textual) [Abstract]
Debt instrument, face amount							50,000,000
GEORGIA POWER CO | Notes Payable to Banks [Member] | Floating Rate Bank Term Loan Agreement 2 [Member]
Financing (Textual) [Abstract]
Debt instrument, face amount									$ 150,000,000						150,000,000
GEORGIA POWER CO | Notes Payable to Banks [Member] | Floating Rate Bank Term Loan Agreement 3 [Member]
Financing (Textual) [Abstract]
Debt instrument, face amount									100,000,000						100,000,000
GEORGIA POWER CO | Capital Lease Obligations
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation			7.90%													7.90%	7.90%	7.90%
GEORGIA POWER CO | Secured Debt
Financing (Textual) [Abstract]
Long-term debt			$ 2,800,000,000														$ 2,800,000,000
GEORGIA POWER CO | Secured Debt | FFB Loan
Financing (Textual) [Abstract]
Long-term debt			2,600,000,000													$ 2,600,000,000	2,600,000,000	$ 2,600,000,000
GEORGIA POWER CO | Senior Notes | Series 2007A Preference Stock [Member]
Financing (Textual) [Abstract]
Stock Redeemed or Called During Period, Shares | shares					2,250,000
Stock Redeemed or Called During Period, Value					$ 225,000,000
Preferred Stock, Dividend Rate, Percentage					6.50%
GEORGIA POWER CO | Senior Notes | Series 2016B
Financing (Textual) [Abstract]
Debt instrument, face amount																											$ 400,000,000
Fixed stated interest rate of debt obligation																											3.25%
GEORGIA POWER CO | Senior Notes | Series 2016A
Financing (Textual) [Abstract]
Debt instrument, face amount																											$ 450,000,000
Fixed stated interest rate of debt obligation																											2.00%
GEORGIA POWER CO | Senior Notes | Series 2017C
Financing (Textual) [Abstract]
Debt instrument, face amount							$ 500,000,000
Fixed stated interest rate of debt obligation							2.00%
GEORGIA POWER CO | Senior Notes | Preferred Class A [Member]
Financing (Textual) [Abstract]
Stock Redeemed or Called During Period, Shares | shares					1,800,000
Stock Redeemed or Called During Period, Value					$ 45,000,000
Preferred Stock, Dividend Rate, Percentage					6.125%
GEORGIA POWER CO | Junior Subordinated Debt
Financing (Textual) [Abstract]
Long-term debt			270,000,000													0	270,000,000	0
GEORGIA POWER CO | Junior Subordinated Debt | Series 2017A [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation						5.00%
GEORGIA POWER CO | Line of Credit | Uncommitted Bank Credit Arrangement [Member]
Financing (Textual) [Abstract]
Repayments of debt			250,000,000				$ 250,000,000
Proceeds from Issuance of Debt									500,000,000
GEORGIA POWER CO | Plant Vogtle Units 3 And 4
Financing (Textual) [Abstract]
Percent ownership		45.70%
GULF POWER CO
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations, Current			0													87,000,000	0	87,000,000
2022			141,000,000														141,000,000
Financing (Textual) [Abstract]
Other long-term debt			309,000,000													309,000,000	309,000,000	309,000,000
2018			0														0
2019			$ 0														$ 0
Bank loans																100,000,000		100,000,000
Ratio of indebtedness to capitalization, debt covenant, required			65.00%														65.00%
Line of credit facility, amount available to support variable rate pollution control revenue bonds			$ 82,000,000														$ 82,000,000
Senior notes			990,000,000													777,000,000	990,000,000	777,000,000
Secured debt			41,000,000													41,000,000	41,000,000	41,000,000
Pollution control revenue bonds, outstanding			309,000,000													309,000,000	309,000,000	309,000,000
Repayments of senior debt																	85,000,000	235,000,000	60,000,000
Accumulated depreciation PPE			1,461,000,000													1,382,000,000	1,461,000,000	1,382,000,000
Unused credit with banks			280,000,000														280,000,000
Short term borrowings excluding other energy service contracts																268,000,000		268,000,000
Pollution control revenue bonds required to be remarketed			$ 75,000,000														75,000,000
Common stock, shares issued | shares												1,750,000
Common stock												$ 175,000,000					$ 175,000,000	0	20,000,000
Number of issuance pollution control revenue bonds | series			2														2
Short-term debt			$ 45,000,000													268,000,000	$ 45,000,000	268,000,000
Commitment fee percentage (less than 1/4 of 1%)																	0.25%
Line of credit facility, maximum borrowing capacity			280,000,000	$ 195,000,000													$ 280,000,000
2020			175,000,000													175,000,000	175,000,000	175,000,000
2021			0														0
Capital contributions from parent company																	2,000,000	20,000,000	4,000,000
Expires, 2018			30,000,000														30,000,000
Line Of Credit Expire Year Three			225,000,000														225,000,000
Assets			4,797,000,000													4,822,000,000	4,797,000,000	4,822,000,000
GULF POWER CO | Secured Debt | Plant Daniel
Financing (Textual) [Abstract]
Pollution control revenue bonds, outstanding			41,000,000														41,000,000
GULF POWER CO | Series 2011A
Financing (Textual) [Abstract]
Redemption amount of principal notes										$ 300,000,000
GULF POWER CO | Long-term Debt, Current
Financing (Textual) [Abstract]
2018																87,000,000		87,000,000
GULF POWER CO | Bank Loans [Member]
Financing (Textual) [Abstract]
Debt instrument, face amount									$ 100,000,000						100,000,000
GULF POWER CO | Senior Notes | Series 2007A Preference Stock [Member]
Financing (Textual) [Abstract]
Stock Redeemed or Called During Period, Shares | shares									450,000
Stock Redeemed or Called During Period, Value									$ 45,000,000
Preferred Stock, Dividend Rate, Percentage									6.45%
GULF POWER CO | Senior Notes | Series 2011A
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation										3.30%
GULF POWER CO | Senior Notes | Series 2007A [Member]
Financing (Textual) [Abstract]
Repayments of debt										$ 85,000,000
Fixed stated interest rate of debt obligation										5.90%
GULF POWER CO | Senior Notes | Series Preference Stock [Member]
Financing (Textual) [Abstract]
Stock Redeemed or Called During Period, Shares | shares									550,000
Stock Redeemed or Called During Period, Value									$ 55,000,000
Preferred Stock, Dividend Rate, Percentage									6.00%
GULF POWER CO | Senior Notes | Series 2013A Preference Stock [Member]
Financing (Textual) [Abstract]
Stock Redeemed or Called During Period, Shares | shares									500,000
Stock Redeemed or Called During Period, Value									$ 50,000,000
Preferred Stock, Dividend Rate, Percentage									5.60%
MISSISSIPPI POWER CO
Debt Instrument [Line Items]
Working Capital			911,000,000														911,000,000
Long-term debt affiliated			0													551,000,000	0	551,000,000
Long-term Debt and Capital Lease Obligations, Current			$ 989,000,000													$ 629,000,000	$ 989,000,000	$ 629,000,000
Temporary equity, shares outstanding (in shares) | shares			334,210													334,210	334,210	334,210
Financing (Textual) [Abstract]
Promissory note																	$ 0	$ 0	301,000,000
Other long-term debt			$ 353,000,000													$ 904,000,000	353,000,000	904,000,000
Senior notes, current			0													35,000,000	0	35,000,000
Loans Payable to Bank, Current			900,000,000													0	900,000,000	0
Long term debt and capital lease obligations, maturities in 2017			900,000,000														900,000,000
Long term debt and capital lease obligations, maturities in 2019			125,000,000														125,000,000
Long Term Debt and Capital Lease Obligation Maturities Repayments in 2021			270,000,000														270,000,000
2018			50,000,000													50,000,000	50,000,000	50,000,000
2019			125,000,000													125,000,000	125,000,000	125,000,000
Long-term debt, maturities, repayments of principal after year five			630,000,000													630,000,000	630,000,000	630,000,000
Bank loans			900,000,000													1,200,000,000	900,000,000	1,200,000,000
Bank loans outstanding			$ 900,000,000													1,200,000,000	$ 900,000,000	1,200,000,000
Ratio of indebtedness to capitalization, debt covenant, required			65.00%														65.00%
Senior notes			$ 755,000,000													790,000,000	$ 755,000,000	790,000,000
Pollution control revenue bonds, outstanding			83,000,000													83,000,000	83,000,000	83,000,000
Revenue bond obligations face value																				$ 270,000,000
Fixed stated interest rate of debt obligation																																	7.13%
Repayments of senior debt																	35,000,000	300,000,000	0
Period of nitrogen supply agreement													20 years
Capitalized lease obligations			0													74,000,000	0	74,000,000
Capital leases, due 2017			7,000,000														7,000,000
Capital leases, due 2019			7,000,000														7,000,000
Capital leases, due 2020			7,000,000														7,000,000
Capital leases, due 2021			7,000,000														7,000,000
Capital leases, due 2022			7,000,000														7,000,000
Accumulated depreciation PPE			1,325,000,000													1,289,000,000	1,325,000,000	1,289,000,000
Unused credit with banks			100,000,000														100,000,000
Amount of variable rate pollution control revenue bonds outstanding requiring liquidity support			40,000,000														40,000,000
Fixed Rate Pollution Control Revenue Bonds Outstanding, Amount Remarketed			50,000,000														50,000,000
Pollution control revenue bonds			$ 40,000,000														$ 40,000,000
Redemption price of redeemable preferred stock, as a percent of liquidation amount			100.00%														100.00%
Short-term debt			$ 4,000,000													$ 23,000,000	$ 4,000,000	$ 23,000,000
Commitment fee percentage (less than 1/4 of 1%)																	0.25%
Line of credit facility, maximum borrowing capacity			$ 100,000,000														$ 100,000,000
Preferred Stock, Par or Stated Value Per Share | $ / shares			$ 100													$ 100	$ 100	$ 100
Temporary Equity, Shares Authorized | shares			1,244,139													1,244,139	1,244,139	1,244,139
Capitalized leases			$ 0													$ 3,000,000	$ 0	$ 3,000,000
Unamortized debt issuance expense			(1,000,000)													0	(1,000,000)	0
Revenue bonds, current			50,000,000														50,000,000
Capital contributions from parent company									$ 1,000,000,000								1,002,000,000	627,000,000	277,000,000
Expires, 2018			100,000,000														100,000,000
Line Of Credit Expire Year Three			0														0
Assets			4,866,000,000													8,235,000,000	4,866,000,000	8,235,000,000
Unsecured debt, current			900,000,000														900,000,000
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Three			0														0
Long term debt and capital lease obligation maturities repayments in year five			0														0
MISSISSIPPI POWER CO | Kemper IGCC
Financing (Textual) [Abstract]
Capitalized lease obligations																$ 74,000,000		$ 74,000,000
MISSISSIPPI POWER CO | Plant Daniel Units 3 and 4
Financing (Textual) [Abstract]
Revenue bond obligations face value																			270,000,000
Significant acquisitions and disposals, acquisition costs, assumption of debt, at fair value																																$ 346,000,000
Fair value adjustment at date of purchase																																$ 76,000,000
MISSISSIPPI POWER CO | Series 1999A
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																																7.13%
MISSISSIPPI POWER CO | Promissory Notes | Promissory Notes
Financing (Textual) [Abstract]
Repayments of debt						$ 109,000,000			591,000,000
Debt instrument, face amount						150,000,000
Proceeds from Issuance of Debt															40,000,000
MISSISSIPPI POWER CO | Capital Lease Obligations
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																4.90%		4.90%
MISSISSIPPI POWER CO | Senior Notes
Financing (Textual) [Abstract]
Redemption amount of principal notes																														$ 300,000,000
MISSISSIPPI POWER CO | Unsecured Debt
Financing (Textual) [Abstract]
Line of credit facility, maximum borrowing capacity																														$ 1,200,000,000
MISSISSIPPI POWER CO | Unsecured Debt | Term Loan [Member]
Financing (Textual) [Abstract]
Repayments of debt									300,000,000
Debt instrument, face amount									1,200,000,000						$ 1,200,000,000
SOUTHERN Co GAS
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations, Current			157,000,000													$ 22,000,000	157,000,000	$ 22,000,000
Repayments of First Mortgage Bond																0	0
2022			93,000,000														93,000,000
Financing (Textual) [Abstract]
Other long-term debt			1,225,000,000													825,000,000	1,225,000,000	825,000,000
2018			155,000,000														155,000,000
2019			350,000,000														350,000,000
Long-term debt, maturities, repayments of principal after year five			$ 4,600,000,000														$ 4,600,000,000
Ratio of indebtedness to capitalization, debt covenant, required			70.00%														70.00%
Senior notes			$ 4,200,000,000													3,700,000,000	$ 4,200,000,000	3,700,000,000
Repayments of senior debt																420,000,000	0
Accumulated depreciation PPE			4,596,000,000													4,439,000,000	4,596,000,000	4,439,000,000
Unused credit with banks			1,890,000,000														1,890,000,000
Short-term debt			1,518,000,000													1,257,000,000	1,518,000,000	1,257,000,000
Line of credit facility, maximum borrowing capacity			1,900,000,000														1,900,000,000
2020			0														0
2021			330,000,000														$ 330,000,000
Restrictions on payment of dividends to parent																	70.00%
Retained earnings, unappropriated			719,000,000														$ 719,000,000
Gas facility revenue bonds			200,000,000													200,000,000	200,000,000	200,000,000
Capital contributions from parent company																1,085,000,000	103,000,000
Expires, 2018			0														0
Line Of Credit Expire Year Three			0														0
Assets			22,987,000,000													21,853,000,000	22,987,000,000	21,853,000,000
SOUTHERN Co GAS | Medium-term Notes
Financing (Textual) [Abstract]
2018			157,000,000														157,000,000
SOUTHERN Co GAS | First Mortgage Bonds And Senior Notes
Financing (Textual) [Abstract]
2018			22,000,000														$ 22,000,000
SOUTHERN Co GAS | Gas Facility Revenue Bonds
Financing (Textual) [Abstract]
Debt instrument, number of series issued | series																	5
Elizabeth Gas
Financing (Textual) [Abstract]
Gas facility revenue bonds			180,000,000														$ 180,000,000
Atlanta Gas Light | Medium-term Notes
Financing (Textual) [Abstract]
Repayments of debt								$ 22,000,000
Long-term debt			$ 159,000,000													181,000,000	$ 159,000,000	181,000,000
Mississippi Power and Southern Power
Financing (Textual) [Abstract]
Ratio of indebtedness to capitalization, debt covenant, required			65.00%														65.00%
Southern Power and Traditional Operating Companies | Senior Notes
Financing (Textual) [Abstract]
Debt instrument, face amount			$ 3,700,000,000														$ 3,700,000,000
SOUTHERN POWER CO
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations, Current			770,000,000													560,000,000	770,000,000	560,000,000
Financing (Textual) [Abstract]
Line of credit facility, current borrowing capacity			22,000,000													78,000,000	22,000,000	78,000,000
2018			770,000,000														770,000,000
2019			600,000,000														600,000,000
Repayments of debt						40,000,000
Bank loans			$ 420,000,000													380,000,000	$ 420,000,000	380,000,000
Ratio of indebtedness to capitalization, debt covenant, required			65.00%														65.00%
Senior notes			$ 5,500,000,000													5,300,000,000	$ 5,500,000,000	5,300,000,000
Secured debt			0														0
Repayments of senior debt																	500,000,000	200,000,000	525,000,000
Accumulated depreciation PPE			1,910,000,000													1,484,000,000	1,910,000,000	1,484,000,000
Unused credit with banks			728,000,000													522,000,000	728,000,000	522,000,000
Short-term debt			105,000,000													209,000,000	$ 105,000,000	209,000,000
Commitment fee percentage (less than 1/4 of 1%)																	0.25%
Line of credit facility, maximum borrowing capacity			750,000,000														$ 750,000,000									600,000,000
2020			825,000,000														825,000,000
2021			300,000,000														300,000,000
Capital contributions from parent company																	0	1,850,000,000	$ 646,000,000
Expires, 2018			0														0
Line Of Credit Expire Year Three			0														0
Assets			15,206,000,000													15,169,000,000	15,206,000,000	$ 15,169,000,000
Long term debt and capital lease obligation maturities repayments in year five			677,000,000														677,000,000
SOUTHERN POWER CO | Minimum
Financing (Textual) [Abstract]
Life output of plant																		10 years
SOUTHERN POWER CO | Maximum
Financing (Textual) [Abstract]
Life output of plant																		20 years
SOUTHERN POWER CO | Bank Loans, Current
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations, Current			420,000,000													60,000,000	420,000,000	$ 60,000,000
SOUTHERN POWER CO | Senior Notes, Current
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations, Current			350,000,000													500,000,000	350,000,000	500,000,000
SOUTHERN POWER CO | Notes Payable to TRE
Financing (Textual) [Abstract]
Other Long-term Debt																1,000,000		1,000,000
SOUTHERN POWER CO | Notes Payable to Banks [Member] | Floating Rate Bank Loan [Member]
Financing (Textual) [Abstract]
Debt instrument, face amount			100,000,000			$ 100,000,000											100,000,000							$ 60,000,000
SOUTHERN POWER CO | Senior Notes | Floating Rate Senior Notes
Financing (Textual) [Abstract]
Debt instrument, face amount				$ 525,000,000
SOUTHERN POWER CO | Senior Notes | Series 2015D 1.85% Senior Notes
Financing (Textual) [Abstract]
Stock Redeemed or Called During Period, Shares | shares				500,000,000
SOUTHERN POWER CO | Senior Notes | Series 2017A [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation				1.85%
Southern Company And Subsidiaries | Senior Notes
Financing (Textual) [Abstract]
Debt instrument, face amount			4,000,000,000														4,000,000,000
Traditional Operating Companies
Financing (Textual) [Abstract]
Pollution control revenue bonds, outstanding			3,300,000,000													3,300,000,000	3,300,000,000	3,300,000,000
Southern Company Gas Capital
Debt Instrument [Line Items]
Line of Credit Terminated										$ 1,300,000,000
Financing (Textual) [Abstract]
Unused credit with banks			1,390,000,000														1,390,000,000
Expires, 2018										1,400,000,000
Southern Company Gas Capital | First Mortgage Bonds Due 2026
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																												4.40%
Southern Company Gas Capital | Senior Notes And Pollution Control Bond | Senior Notes Due 2076
Financing (Textual) [Abstract]
Debt instrument, face amount																													$ 450,000,000
Nicor Gas
Debt Instrument [Line Items]
Line of Credit Terminated										700,000,000
Financing (Textual) [Abstract]
Unused credit with banks			500,000,000														500,000,000
First mortgage bonds			1,000,000,000													625,000,000	1,000,000,000	625,000,000
Expires, 2018										$ 500,000,000
Nicor Gas | First Mortgage Bonds Due 2027
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																									3.03%
First mortgage bonds																									$ 100,000,000
Nicor Gas | First Mortgage Bonds Due 2037
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																									3.62%
First mortgage bonds																									$ 100,000,000
Nicor Gas | First Mortgage Bonds Due 2047
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																						3.85%
First mortgage bonds																						$ 100,000,000
Nicor Gas | First Mortgage Bonds Due 2057
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																						4.00%
First mortgage bonds																						$ 100,000,000
Southern Natural Gas Company, LLC | SOUTHERN Co GAS
Debt Instrument [Line Items]
Ownership percentage, equity method investment																												50.00%
Capital Lease Obligations | GEORGIA POWER CO | Secured Debt
Financing (Textual) [Abstract]
Long-term debt			$ 154,000,000													$ 169,000,000	$ 154,000,000	$ 169,000,000
Redeemable Preferred Stock Type One [Member]
Debt Instrument [Line Items]
Temporary equity, shares outstanding (in shares) | shares			1,000,000													1,000,000	1,000,000	1,000,000
Financing (Textual) [Abstract]
Preferred Stock, Par or Stated Value Per Share | $ / shares			$ 100													$ 100	$ 100	$ 100
Temporary Equity, Shares Authorized | shares			20,000,000													20,000,000	20,000,000	20,000,000
Redeemable Preferred Stock Type One [Member] | ALABAMA POWER CO
Debt Instrument [Line Items]
Temporary equity, shares outstanding (in shares) | shares			475,115													475,115	475,115	475,115
Financing (Textual) [Abstract]
Preferred Stock, Par or Stated Value Per Share | $ / shares			$ 100													$ 100	$ 100	$ 100
Temporary Equity, Shares Authorized | shares			3,850,000													3,850,000	3,850,000	3,850,000
Redeemable Preferred Stock Type One [Member] | GULF POWER CO
Financing (Textual) [Abstract]
Temporary Equity, Shares Authorized | shares			0														0
Redeemable Preferred Stock Type Two [Member]
Debt Instrument [Line Items]
Temporary equity, shares outstanding (in shares) | shares			0													2,000,000	0	2,000,000
Financing (Textual) [Abstract]
Preferred Stock, Par or Stated Value Per Share | $ / shares			$ 1													$ 1	$ 1	$ 1
Temporary Equity, Shares Authorized | shares			28,000,000													28,000,000	28,000,000	28,000,000
Redeemable Preferred Stock Type Two [Member] | ALABAMA POWER CO
Debt Instrument [Line Items]
Temporary equity, shares outstanding (in shares) | shares			10,000,000													1,520,000	10,000,000	1,520,000
Financing (Textual) [Abstract]
Preferred Stock, Par or Stated Value Per Share | $ / shares			$ 1													$ 1	$ 1	$ 1
Temporary Equity, Shares Authorized | shares			27,500,000													27,500,000	27,500,000	27,500,000
Redeemable Preferred Stock Type Two [Member] | GULF POWER CO
Debt Instrument [Line Items]
Temporary equity, shares outstanding (in shares) | shares			0														0
Preferred Class A [Member] | GEORGIA POWER CO
Financing (Textual) [Abstract]
Preference stock, shares outstanding | shares			0														0
5.00% Class A Preferred Stock | ALABAMA POWER CO
Debt Instrument [Line Items]
Temporary equity, shares outstanding (in shares) | shares			10,000,000			10,000,000											10,000,000
Financing (Textual) [Abstract]
Temporary equity, dividend rate percentage						0.05											0.0500
Preferred Stock, Par or Stated Value Per Share | $ / shares			$ 1														$ 1
Par value/stated capital per share (in dollars per share) | $ / shares			$ 25			$ 25											$ 25
5.00% Class A Preferred Stock | ALABAMA POWER CO | Aggregate Stated Capital [Member]
Financing (Textual) [Abstract]
Debt instrument, face amount						$ 250,000,000
5.30% Class A Preferred Stock | ALABAMA POWER CO
Debt Instrument [Line Items]
Temporary equity, shares outstanding (in shares) | shares						2,000,000
Financing (Textual) [Abstract]
Temporary equity, dividend rate percentage						0.065											0.0530
5.30% Class A Preferred Stock | ALABAMA POWER CO | Aggregate Stated Capital [Member]
Financing (Textual) [Abstract]
Debt instrument, face amount						$ 50,000,000
5.625% Preference Stock | ALABAMA POWER CO
Debt Instrument [Line Items]
Temporary equity, shares outstanding (in shares) | shares						6,000,000
Financing (Textual) [Abstract]
Temporary equity, dividend rate percentage						0.0645											0.05625
5.625% Preference Stock | ALABAMA POWER CO | Aggregate Stated Capital [Member]
Financing (Textual) [Abstract]
Debt instrument, face amount						$ 150,000,000
5.83% Class A Preferred Stock | ALABAMA POWER CO
Debt Instrument [Line Items]
Temporary equity, shares outstanding (in shares) | shares						1,500,000
Financing (Textual) [Abstract]
Temporary equity, dividend rate percentage						0.0583											0.0583
5.83% Class A Preferred Stock | ALABAMA POWER CO | Aggregate Stated Capital [Member]
Financing (Textual) [Abstract]
Debt instrument, face amount						$ 38,000,000
Preference Stock | GEORGIA POWER CO
Financing (Textual) [Abstract]
Preference stock, shares outstanding | shares			0														0
Noncumulative Preferred Stock [Member]
Financing (Textual) [Abstract]
Preferred Stock, Par or Stated Value Per Share | $ / shares			$ 25													$ 25	$ 25	$ 25
Preference stock, shares outstanding | shares			0													2,000,000	0	2,000,000
Noncumulative Preferred Stock [Member] | ALABAMA POWER CO
Financing (Textual) [Abstract]
Preferred Stock, Par or Stated Value Per Share | $ / shares			$ 25													$ 25	$ 25	$ 25
Preference stock, shares outstanding | shares			0													8,000,000	0	8,000,000
Noncumulative Preferred Stock [Member] | GULF POWER CO
Financing (Textual) [Abstract]
Preference stock, shares outstanding | shares			0														0
Loans Payable [Member] | MISSISSIPPI POWER CO | Bank Loans [Member]
Financing (Textual) [Abstract]
Repayments of debt									$ 10,000,000
Notes Payable to Banks [Member] | MISSISSIPPI POWER CO | Notes Payable to Banks [Member]
Financing (Textual) [Abstract]
Repayments of debt							$ 12,500,000
Short Term Note [Member] | MISSISSIPPI POWER CO
Financing (Textual) [Abstract]
Debt instrument, face amount																											$ 9,000,000
Fixed stated interest rate of debt obligation																											5.00%
Commercial Paper
Financing (Textual) [Abstract]
Short term borrowings excluding other energy service contracts			$ 1,832,000,000													$ 1,909,000,000	$ 1,832,000,000	$ 1,909,000,000
Commercial Paper | GEORGIA POWER CO
Financing (Textual) [Abstract]
Short term borrowings excluding other energy service contracts																392,000,000		392,000,000
Commercial Paper | GULF POWER CO
Financing (Textual) [Abstract]
Short term borrowings excluding other energy service contracts			45,000,000													168,000,000	45,000,000	168,000,000
Commercial Paper | MISSISSIPPI POWER CO
Financing (Textual) [Abstract]
Short term borrowings excluding other energy service contracts			0													0	0	0
Commercial Paper | SOUTHERN Co GAS
Financing (Textual) [Abstract]
Short term borrowings excluding other energy service contracts			1,518,000,000													1,257,000,000	1,518,000,000	1,257,000,000
Commercial Paper | SOUTHERN POWER CO
Financing (Textual) [Abstract]
Short term borrowings excluding other energy service contracts			105,000,000													0	105,000,000	0
Commercial Paper | Southern Company Gas Capital
Financing (Textual) [Abstract]
Short term borrowings excluding other energy service contracts			1,243,000,000													733,000,000	1,243,000,000	733,000,000
Commercial Paper | Nicor Gas
Financing (Textual) [Abstract]
Short term borrowings excluding other energy service contracts			275,000,000													524,000,000	275,000,000	524,000,000
Long-term Debt | Parent Company
Financing (Textual) [Abstract]
Bank loans			1,500,000,000													2,000,000,000	1,500,000,000	2,000,000,000
Short-term Debt | Parent Company
Financing (Textual) [Abstract]
Bank loans			600,000,000													100,000,000	600,000,000	100,000,000
Power Purchase Agreement | GEORGIA POWER CO
Financing (Textual) [Abstract]
Capital leased assets, gross			144,000,000													149,000,000	144,000,000	149,000,000
Capitalized lease obligations			$ 132,000,000													141,000,000	$ 132,000,000	141,000,000
Capital leased assets, number of units | leased_asset_units			2														2
Accumulated depreciation PPE			$ 29,000,000													19,000,000	$ 29,000,000	19,000,000
Power Purchase Agreement | GEORGIA POWER CO | Minimum
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation			10.00%														10.00%
Power Purchase Agreement | GEORGIA POWER CO | Maximum
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation			12.00%														12.00%
Line of Credit
Financing (Textual) [Abstract]
Line of credit facility, maximum borrowing capacity			$ 2,000,000,000.0														$ 2,000,000,000.0									$ 1,250,000,000.00
FFB Loan | GEORGIA POWER CO
Financing (Textual) [Abstract]
Line of credit facility, maximum borrowing capacity			2,600,000,000													2,600,000,000	2,600,000,000	2,600,000,000
Continuing Letter of Credit Facility | SOUTHERN POWER CO
Financing (Textual) [Abstract]
Unused credit with banks			82,000,000														82,000,000
Line of credit facility, maximum borrowing capacity			120,000,000														120,000,000
Power Purchase Agreement | SOUTHERN POWER CO
Financing (Textual) [Abstract]
Unused credit with banks			19,000,000														19,000,000
Long-term Line of Credit			101,000,000														101,000,000
Debt instrument, collateral amount			113,000,000														113,000,000
Construction Loan And Bridge Loan | SOUTHERN POWER CO
Financing (Textual) [Abstract]
Line of credit facility, current borrowing capacity			0													$ 209,000,000	0	$ 209,000,000
Debt, weighted average interest rate																2.10%		2.10%
Southern Company Gas Capital | SOUTHERN Co GAS
Debt Instrument [Line Items]
Noncontrolling ownership percentage held by parent																100.00%		100.00%
Parent Company | MISSISSIPPI POWER CO
Financing (Textual) [Abstract]
Promissory note											$ 551,000,000						551,000,000
RE Roserock, LLC | SOUTHERN POWER CO
Financing (Textual) [Abstract]
Percentage of voting interests acquired																			51.00%
Withholding of construction contract payments																	26,000,000		$ 26,000,000
Mankato | SOUTHERN POWER CO
Debt Instrument [Line Items]
Noncontrolling ownership percentage held by parent	100.00%
Financing (Textual) [Abstract]
Life output of plant	10 years
Senior Lien | SOUTHERN POWER CO
Financing (Textual) [Abstract]
Assets			$ 442,000,000														$ 442,000,000
Chevron Products Company | MISSISSIPPI POWER CO
Financing (Textual) [Abstract]
Co-generation Assets, Net																							$ 93,000,000