Financing - Textual (Details)										1 Months Ended						12 Months Ended
	Feb. 21, 2017 USD ($) shares	Dec. 14, 2016 USD ($)	Oct. 26, 2016	Jun. 27, 2016 USD ($)	Mar. 08, 2016 USD ($)	Jan. 28, 2016 USD ($)	Jul. 15, 2015 USD ($)	Jun. 03, 2015 USD ($)	Feb. 20, 2014 USD ($)	Sep. 30, 2016 USD ($)	May 31, 2016 USD ($)	Feb. 29, 2016 USD ($)	May 31, 2015 USD ($) $ / shares shares	Jan. 31, 2015 USD ($)	Sep. 30, 2013	Dec. 31, 2016 USD ($) leased_asset_units series shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2016 EUR (€) leased_asset_units series shares	Oct. 07, 2016 USD ($)	Sep. 01, 2016	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Jan. 31, 2016 USD ($)	Jan. 19, 2016 USD ($)	Aug. 31, 2015 USD ($)	Jan. 01, 2015 shares	Dec. 31, 2013
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations, Current																$ 2,587,000,000	$ 2,674,000,000
2021																2,655,000,000	200,000,000
Redeemable preferred stock																118,000,000	118,000,000	$ 375,000,000
Financing (Textual) [Abstract]
Proceeds from issuance of junior subordinated notes																206,000,000	206,000,000
Other Long-term Debt																9,404,000,000	6,808,000,000
Senior notes, current																1,995,000,000	1,810,000,000
Other Long-term Debt																485,000,000	829,000,000
Long term debt and capital lease obligations, maturities in 2014																2,600,000,000
Long term debt and capital lease obligations, maturities in 2015																3,900,000,000
Long term debt and capital lease obligations, maturities in 2016																3,200,000,000
Long Term Debt and Capital Lease Obligation Maturities Repayments in Year Four																1,400,000,000
Long term debt and capital lease obligations, maturities in 2018																3,100,000,000
2017																2,019,000,000	1,995,000,000
2018																2,353,000,000	1,697,000,000
Long-term Debt, Maturities, Repayments of Principal after Year Five																21,797,000,000	10,972,000,000
2019																$ 3,076,000,000	1,176,000,000
Ratio of indebtedness to capitalization, debt covenant, required																70.00%				70.00%							65.00%
Senior Notes outstanding																$ 33,000,000,000	19,100,000,000
Capitalized lease obligations																136,000,000	146,000,000
Accumulated depreciation PPE																29,852,000,000	24,253,000,000
Unused credit with banks																8,273,000,000
Amount of Variable Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support																1,900,000,000
Short Term Borrowings Excluding Other Energy Service Contracts																2,032,000,000	1,240,000,000
Remarketed pollution control bonds																400,000,000
Long-term Pollution Control Bond, Current																76,000,000	$ 4,000,000
Expires, 2020																$ 4,400,000,000
Common Stock, Shares, Issued | shares																991,000,000	915,000,000			991,000,000
Common stock issuances																$ 3,758,000,000	$ 256,000,000	806,000,000
Short-term debt																$ 2,241,000,000	1,376,000,000
Commitment fee percentage (less than 1/4 of 1%)																0.25%
Line of Credit Facility, Maximum Borrowing Capacity																$ 8,443,000,000
2020																1,326,000,000	1,327,000,000
Line of Credit Expire Year One																423,000,000
Assets																109,697,000,000	78,318,000,000	70,233,000,000
Building [Member]
Financing (Textual) [Abstract]
Capital leased assets, gross																61,000,000	61,000,000
Maturity of Junior Subordinated Notes Due Two Thousand Seventy Five [Member]
Financing (Textual) [Abstract]
Junior subordinated notes																2,350,000,000	1,000,000,000
Trust Preferred Securities Subject to Mandatory Redemption [Member]
Financing (Textual) [Abstract]
Preferred securities, outstanding																200,000,000	200,000,000
Senior Notes [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount																8,500,000,000.0
Georgia Power [Member]
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations, Current																460,000,000	712,000,000
Financing (Textual) [Abstract]
Line of Credit Facility, Current Borrowing Capacity																125,000,000							$ 300,000,000
Other Long-term Debt																4,445,000,000	4,024,000,000
Senior notes, current																450,000,000	700,000,000
Long term debt and capital lease obligations, maturities in 2014																460,000,000
Long term debt and capital lease obligations, maturities in 2015																762,000,000
Long term debt and capital lease obligations, maturities in 2016																513,000,000
Long Term Debt and Capital Lease Obligation Maturities Repayments in Year Four																57,000,000
Long term debt and capital lease obligations, maturities in 2018																376,000,000
2017																450,000,000	450,000,000
2018																748,000,000	747,000,000
Long-term Debt, Maturities, Repayments of Principal after Year Five																4,175,000,000	3,850,000,000
2019																$ 500,000,000	502,000,000
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%
Payments of Debt Issuance Costs																		66,000,000
Senior Notes outstanding																$ 6,200,000,000	6,300,000,000
Amortization Period For Line Of Credit Facility									5 years
Pollution control revenue bonds, outstanding																1,800,000,000	1,800,000,000
Repayments of Senior Debt																700,000,000	1,175,000,000	0
Capitalized lease obligations																169,000,000	183,000,000
Accumulated depreciation PPE																11,317,000,000	10,903,000,000
Unused credit with banks																1,732,000,000
Amount of Variable Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support																868,000,000
Pollution Control Revenue Bonds Required To Be Remarketed																250,000,000
Long-term Pollution Control Bond, Current																$ 0	4,000,000
Redemption price of redeemable preferred stock, as a percent of liquidation amount																100.00%				100.00%
Expires, 2020																$ 1,750,000,000
Short-term debt																$ 391,000,000	158,000,000
Commitment fee percentage (less than 1/4 of 1%)																0.25%
Line of Credit Facility, Maximum Borrowing Capacity																$ 1,750,000,000
2020																325,000,000	0
Capital contributions from parent company																594,000,000	62,000,000	549,000,000
Line of Credit Expire Year One																0
Assets																34,835,000,000	32,865,000,000
Georgia Power [Member] | Corporate, Non-Segment [Member]
Financing (Textual) [Abstract]
Capital leased assets, gross																61,000,000
Capitalized lease obligations																	61,000,000
Accumulated depreciation PPE																33,000,000	26,000,000
Georgia Power [Member] | Building [Member]
Financing (Textual) [Abstract]
Capitalized lease obligations																$ 28,000,000	$ 35,000,000
Georgia Power [Member] | Line of Credit [Member] | Debt Due Two Thousand Forty Four [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																3.142%				3.142%			2.571%
Georgia Power [Member] | Capital Lease Obligations
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																7.90%	7.90%			7.90%
Georgia Power [Member] | Secured Debt [Member]
Financing (Textual) [Abstract]
Long-term Debt																$ 2,800,000,000	$ 2,400,000,000
Georgia Power [Member] | Secured Debt [Member] | FFB Loan [Member]
Financing (Textual) [Abstract]
Long-term Debt																$ 2,600,000,000	2,200,000,000
Georgia Power [Member] | Senior Notes [Member] | Series 2016B [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount																								$ 325,000,000
Fixed stated interest rate of debt obligation																								2.40%
Georgia Power [Member] | Senior Notes [Member] | Series 2016A [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount																								$ 325,000,000
Fixed stated interest rate of debt obligation																								3.25%
Georgia Power [Member] | Unsecured Debt [Member] | Series 2013B [Member]
Financing (Textual) [Abstract]
Redemption Amount of Principal Notes																								$ 250,000,000
Georgia Power [Member] | Plant Vogtle Units 3 And 4 [Member]
Financing (Textual) [Abstract]
Percent ownership									45.70%
Georgia Power [Member] | Vogtle Units Three and Four [Member]
Financing (Textual) [Abstract]
Percent ownership																45.70%				45.70%
Mississippi Power [Member]
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations, Current																$ 629,000,000	$ 728,000,000
Working Capital																$ 371,000,000
Temporary Equity, Shares Outstanding | shares																334,210	334,210			334,210
Financing (Textual) [Abstract]
Promissory Note						$ 275,000,000		$ 301,000,000								$ 0	$ 301,000,000	0
Line of Credit Facility, Current Borrowing Capacity																100,000,000										$ 100,000,000
Other Long-term Debt																904,000,000	929,000,000
Senior notes, current																35,000,000	300,000,000
Other Long-term Debt																63,000,000
Long term debt and capital lease obligations, maturities in 2014																629,000,000
Long term debt and capital lease obligations, maturities in 2015																1,200,000,000
Long term debt and capital lease obligations, maturities in 2016																128,000,000
Long Term Debt and Capital Lease Obligation Maturities Repayments in Year Four																10,000,000
Long term debt and capital lease obligations, maturities in 2018																274,000,000
2017																35,000,000	35,000,000
Long-term Debt, Maturities, Repayments of Principal after Year Five																680,000,000	680,000,000
2019																125,000,000	125,000,000
Bank Loans																1,200,000,000	900,000,000
Bank loans outstanding																1,200,000,000	900,000,000
Bank term loans																$ 0	425,000,000
Ratio of indebtedness to capitalization, debt covenant, required																65.00%				65.00%
Senior Notes outstanding																$ 790,000,000	1,100,000,000
Pollution control revenue bonds, outstanding																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																300,000,000	0	0
Other revenue bond obligation																50,000,000	50,000,000
Period Of Nitrogen Supply Agreement															20 years
Capitalized lease obligations																74,000,000	77,000,000
Capital leases, due 2017																7,000,000
Capital leases, due 2018																7,000,000
Capital leases, due 2019																7,000,000
Capital leases, due 2020																7,000,000
Capital leases, due 2021																7,000,000
Capital leases, due 2022 and thereafter																7,000,000
Accumulated depreciation PPE																1,289,000,000	1,262,000,000
Unused credit with banks																150,000,000
Amount of Variable Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support																40,000,000
Long-term Pollution Control Bond, Current																$ 40,000,000	0
Redemption price of redeemable preferred stock, as a percent of liquidation amount																100.00%				100.00%
Expires, 2020																$ 0
Short-term debt																$ 23,000,000	500,000,000
Commitment fee percentage (less than 1/4 of 1%)																0.25%
Line of Credit Facility, Maximum Borrowing Capacity																$ 173,000,000
Capital contributions from parent company		$ 400,000,000		$ 225,000,000												627,000,000	277,000,000	451,000,000
Line of Credit Expire Year One																173,000,000
Assets																8,235,000,000	7,840,000,000
Mississippi Power [Member] | Kemper IGCC [Member]
Financing (Textual) [Abstract]
Capitalized lease obligations																$ 74,000,000	$ 77,000,000
Mississippi Power [Member] | Plant Daniel Units 3 and 4 [Member]
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 [Member] | Series 1999A [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																		7.13%
Mississippi Power [Member] | Notes Payable to Banks [Member]
Financing (Textual) [Abstract]
Repayments of Senior Debt					$ 900,000,000
Mississippi Power [Member] | Capital Lease Obligations
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																4.90%	4.90%			4.90%
Mississippi Power [Member] | Senior Notes [Member]
Financing (Textual) [Abstract]
Redemption Amount of Principal Notes					300,000,000
Fixed stated interest rate of debt obligation																							2.35%
Mississippi Power [Member] | Unsecured Debt [Member]
Financing (Textual) [Abstract]
Line of Credit Facility, Current Borrowing Capacity					900,000,000																$ 300,000,000
Line of Credit Facility, Maximum Borrowing Capacity					$ 1,200,000,000
Southern Company Gas [Member]
Debt Instrument [Line Items]
2021																$ 330,000,000
Financing (Textual) [Abstract]
2017																22,000,000
2018																155,000,000
Long-term Debt, Maturities, Repayments of Principal after Year Five																3,900,000,000
2019																$ 350,000,000
Ratio of indebtedness to capitalization, debt covenant, required																70.00%				70.00%
Senior Notes outstanding																$ 3,700,000,000	$ 2,500,000,000
Unused credit with banks																1,949,000,000
Expires, 2020																0
Line of Credit Facility, Maximum Borrowing Capacity																2,000,000,000
2020																$ 0
Restrictions On Payment Of Dividends To Parent																70.00%
Retained Earnings, Unappropriated																$ 688,000,000
First Mortgage Bonds																625,000,000	375,000,000
Gas Facility Revenue Bonds																200,000,000	200,000,000
Line of Credit Expire Year One																75,000,000
Southern Company Gas [Member] | Medium-term Notes [Member]
Financing (Textual) [Abstract]
2017																22,000,000
Southern Company Gas [Member] | Senior Notes Due 2026 [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation										3.95%	3.25%
Southern Company Gas [Member] | Senior Notes Due 2016 [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation											6.375%
Southern Company Gas [Member] | Senior Notes Due 2023 [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation											2.45%
Southern Company Gas [Member] | First Mortgage Bonds And Senior Notes [Member]
Financing (Textual) [Abstract]
2017																$ 545,000,000
Southern Company Gas [Member] | Senior Notes Due October 2018 [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																3.50%				3.50%
Southern Company Gas [Member] | Promissory Note [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount										$ 360,000,000
Southern Company Gas [Member] | Callable Debt [Member]
Financing (Textual) [Abstract]
Long-term Debt, Current Maturities																$ 120,000,000							$ 275,000,000
Long-term Debt																$ 155,000,000
Southern Company Gas [Member] | Gas Facility Revenue Bonds [Member]
Financing (Textual) [Abstract]
Debt Instrument, Number of Series Issued | series																5
Southern Company Gas [Member] | Senior Notes [Member] | Senior Notes Due 2026 [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount										550,000,000	$ 350,000,000
Southern Company Gas [Member] | Senior Notes [Member] | Senior Notes Due 2016 [Member]
Financing (Textual) [Abstract]
Repayments of Senior Debt										120,000,000	300,000,000
Southern Company Gas [Member] | Senior Notes [Member] | Senior Notes Due 2023 [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount										350,000,000
Southern Company Gas [Member] | Medium-term Notes [Member]
Financing (Textual) [Abstract]
Long-term Debt																$ 159,000,000	181,000,000
Gulf Power [Member]
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations, Current																87,000,000	110,000,000
2021																0
Financing (Textual) [Abstract]
Other Long-term Debt																309,000,000	309,000,000
2017																87,000,000	85,000,000
2018																0
Long-term Debt, Maturities, Repayments of Principal after Year Five																515,000,000	640,000,000
2019																0
Bank Loans																$ 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
Senior Notes outstanding																777,000,000	1,010,000,000
Secured Debt																41,000,000	41,000,000
Pollution control revenue bonds, outstanding																309,000,000	309,000,000
Repayments of Senior Debt																235,000,000	60,000,000	$ 75,000,000
Accumulated depreciation PPE																1,382,000,000	1,296,000,000
Unused credit with banks																280,000,000
Short Term Borrowings Excluding Other Energy Service Contracts																268,000,000
Pollution Control Revenue Bonds Required To Be Remarketed																$ 86,000,000
Redemption price of redeemable preferred stock, as a percent of liquidation amount																100.00%				100.00%
Expires, 2020																$ 0
Common Stock, Shares, Issued | shares																												200,000
Common stock issuances														$ 20,000,000		$ 0	20,000,000	50,000,000
Number of Issuance Pollution Control Revenue Bonds | series																2				2
Short-term debt																$ 268,000,000	142,000,000
Commitment fee percentage (less than 1/4 of 1%)																0.25%
Line of Credit Facility, Maximum Borrowing Capacity																$ 280,000,000
2020																175,000,000	175,000,000
Capital contributions from parent company																20,000,000	4,000,000	4,000,000
Line of Credit Expire Year One																85,000,000
Assets																$ 4,822,000,000	4,920,000,000
Gulf Power [Member] | Subsequent Event [Member]
Financing (Textual) [Abstract]
Common Stock, Shares, Issued | shares	1,750,000
Common stock issuances	$ 175,000,000
Gulf Power [Member] | Minimum [Member]
Financing (Textual) [Abstract]
Redeemable preferred stock, redemption period																5 years
Gulf Power [Member] | Maximum [Member]
Financing (Textual) [Abstract]
Redeemable preferred stock, redemption period																10 years
Gulf Power [Member] | Secured Debt [Member] | Plant Daniel [Member]
Financing (Textual) [Abstract]
Pollution control revenue bonds, outstanding																$ 41,000,000
Gulf Power [Member] | Series 2011A [Member]
Financing (Textual) [Abstract]
Redemption Amount of Principal Notes											$ 125,000,000
Gulf Power [Member] | Long-term Debt, Current [Member]
Financing (Textual) [Abstract]
2017																	110,000,000
Gulf Power [Member] | Bank Loans [Member]
Debt Instrument [Line Items]
Debt Instrument, Term											11 months
Financing (Textual) [Abstract]
Debt Instrument, Face Amount											$ 100,000,000
Gulf Power [Member] | Senior Notes [Member] | Series 2011A [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation											5.75%
Alabama Power [Member]
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations, Current																561,000,000	200,000,000
2021																$ 220,000,000	200,000,000
Ownership percentage, equity method investment																50.00%				50.00%
Redeemable preferred stock																$ 85,000,000	85,000,000
Senior Notes And Pollution Control Revenue Bonds, Current																561,000,000	200,000,000
Financing (Textual) [Abstract]
Proceeds from issuance of junior subordinated notes																206,000,000	206,000,000
Other Long-term Debt																1,096,000,000	1,097,000,000
2017																525,000,000	525,000,000
Long-term Debt, Maturities, Repayments of Principal after Year Five																4,625,000,000	4,225,000,000
2019																200,000,000	200,000,000
Bank Loans																$ 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																$ 1,100,000,000	1,100,000,000
Repayments of Senior Debt																200,000,000	650,000,000	0
Capitalized lease obligations																4,000,000	5,000,000
Accumulated depreciation PPE																9,112,000,000	8,736,000,000
Unused credit with banks																1,335,000,000
Amount of Variable Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support																890,000,000
Pollution Control Revenue Bonds Required To Be Remarketed																87,000,000
Short-term debt outstanding, regulatory approved maximum																2,100,000,000
Expires, 2020																800,000,000
Short-term debt																$ 0	0
Commitment fee percentage (less than 1/4 of 1%)																0.10%
Line of Credit Facility, Maximum Borrowing Capacity																$ 1,335,000,000
Temporary Equity, Other Changes													$ 5,000,000
2020																250,000,000	250,000,000
Capital contributions from parent company																260,000,000	22,000,000	28,000,000
Line of Credit Expire Year One																35,000,000
Assets																22,516,000,000	21,721,000,000
Alabama Power [Member] | Trust Preferred Securities Subject to Mandatory Redemption [Member]
Financing (Textual) [Abstract]
Preferred securities, outstanding																200,000,000	$ 200,000,000
Alabama Power [Member] | Series FF [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																									5.20%
Alabama Power [Member] | Senior Notes And Pollution Control Bond [Member]
Debt Instrument [Line Items]
2021																310,000,000
Financing (Textual) [Abstract]
2017																561,000,000
2018																200,000,000
2019																0
2020																$ 250,000,000
Alabama Power [Member] | Bank Loans [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount																								$ 45,000,000
Fixed stated interest rate of debt obligation																								2.38%
Alabama Power [Member] | Capital Lease Obligations
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																6.90%	6.90%			6.90%
Alabama Power [Member] | Senior Notes [Member] | Series Z [Member] | Subsequent Event [Member]
Financing (Textual) [Abstract]
Redemption Amount of Principal Notes	$ 200,000,000
Fixed stated interest rate of debt obligation	5.55%
Alabama Power [Member] | Senior Notes [Member] | Series 2016A [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount																									$ 400,000,000
Fixed stated interest rate of debt obligation																									4.30%
Alabama Power [Member] | Unsecured Debt [Member]
Financing (Textual) [Abstract]
Redemption Amount of Principal Notes																									$ 200,000,000
Senior Notes outstanding																$ 5,800,000,000	$ 5,600,000,000
Mississippi Power and Southern Power [Member]
Financing (Textual) [Abstract]
Ratio of indebtedness to capitalization, debt covenant, required																65.00%				65.00%
Subsidiaries [Member]
Financing (Textual) [Abstract]
Capitalized lease obligations																$ 29,000,000	30,000,000
Subsidiaries [Member] | Capital Lease Obligations | Minimum [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																1.40%				1.40%
Subsidiaries [Member] | Capital Lease Obligations | Maximum [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																3.40%				3.40%
Southern Power and Traditional Operating Companies [Member] | Senior Notes [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount																$ 4,800,000,000
Southern Power [Member]
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations, Current																560,000,000	403,000,000
Financing (Textual) [Abstract]
Prepayment of debt																6,000,000
Line of Credit Facility, Current Borrowing Capacity																78,000,000	34,000,000
Other Long-term Debt																15,000,000	13,000,000
2017																561,000,000
2018																670,000,000
2019																600,000,000
Bank Loans																$ 380,000,000	400,000,000
Ratio of indebtedness to capitalization, debt covenant, required																65.00%				65.00%
Senior Notes outstanding																$ 5,300,000,000	2,700,000,000
Repayments of Senior Debt																200,000,000	525,000,000	0
Accumulated depreciation PPE																1,484,000,000	1,248,000,000
Unused credit with banks																522,000,000	566,000,000
Expires, 2020																600,000,000
Short-term debt																$ 209,000,000	137,000,000
Commitment fee percentage (less than 1/4 of 1%)																0.25%
Line of Credit Facility, Maximum Borrowing Capacity																$ 600,000,000											$ 600,000,000
2020																300,000,000
Capital contributions from parent company																1,850,000,000	$ 646,000,000	$ 146,000,000
Line of Credit Expire Year One																0
Life Output Of Plant																	20 years
Assets																15,169,000,000	$ 8,905,000,000
Southern Power [Member] | Bank Loans, Current [Member]
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations, Current																60,000,000	400,000,000
Southern Power [Member] | Senior Notes, Current [Member]
Debt Instrument [Line Items]
Long-term Debt and Capital Lease Obligations, Current																500,000,000
Southern Power [Member] | Notes Payable to TRE [Member]
Financing (Textual) [Abstract]
Other Long-term Debt																$ 1,000,000	3,000,000
Southern Power [Member] | Floating Rate Bank Loan [Member]
Financing (Textual) [Abstract]
Ratio of indebtedness to capitalization, debt covenant, required																65.00%				65.00%
Southern Power [Member] | Bank Loans [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount										60,000,000
Repayments of Senior Debt										80,000,000
Southern Power [Member] | Bank Loans [Member] | Debt Due Two Thousand Sixteen [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount										400,000,000
Southern Power [Member] | Bank Loans [Member] | Debt Due Two Thousand Eighteen [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount										$ 320,000,000
Southern Power [Member] | Senior Notes [Member] | Series 2015A [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount													$ 600,000,000
Fixed stated interest rate of debt obligation													1.00%
Southern Power [Member] | Senior Notes [Member] | Series 2015B [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount													$ 500,000,000
Fixed stated interest rate of debt obligation													1.85%
Southern Power [Member] | Senior Notes [Member] | Series Two Thousand Three [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation							2.75%
Repayments of Senior Debt							$ 290,000,000
Southern Power [Member] | Senior Notes [Member] | Series 2016A [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount | €																				€ 600,000,000
Fixed stated interest rate of debt obligation																1.95%				1.95%
Southern Power [Member] | Senior Notes [Member] | Series 2016E [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount | €																				€ 300,000,000
Fixed stated interest rate of debt obligation																2.50%				2.50%
Southern Power [Member] | Senior Notes [Member] | Series 2016F [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount | €																				€ 400,000,000
Fixed stated interest rate of debt obligation																4.95%				4.95%
Southern Power [Member] | Senior Notes [Member] | Series E [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount | €																				€ 200,000,000
Fixed stated interest rate of debt obligation																6.375%				6.375%
Southern Company And Subsidiaries [Member] | Senior Notes [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount																$ 13,300,000,000
Traditional Operating Companies
Financing (Textual) [Abstract]
Pollution control revenue bonds, outstanding																3,300,000,000	3,300,000,000
Southern Company Gas Capital [Member]
Financing (Textual) [Abstract]
Unused credit with banks																1,249,000,000
Line of Credit Facility, Maximum Borrowing Capacity																1,300,000,000
Line of Credit Expire Year One																49,000,000
Nicor Gas [Member]
Financing (Textual) [Abstract]
Unused credit with banks																700,000,000
Line of Credit Facility, Maximum Borrowing Capacity																700,000,000
Line of Credit Expire Year One																26,000,000
Nicor Gas [Member] | Senior Notes And Pollution Control Bond [Member]
Debt Instrument [Line Items]
Repayments of First Mortgage Bond											$ 50,000,000	$ 75,000,000
Nicor Gas [Member] | First Mortgage Bonds Due 2026 [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation										2.66%
Nicor Gas [Member] | First Mortgage Bonds Due 2031 [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation										2.91%
Nicor Gas [Member] | First Mortgage Bonds Due 2036 [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																							3.27%
Nicor Gas [Member] | Senior Notes And Pollution Control Bond [Member] | Senior Notes Due Two Thousand Seventy Six [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount																							$ 250,000,000
Nicor Gas [Member] | Senior Notes And Pollution Control Bond [Member] | First Mortgage Bonds Due 2026 [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount																							100,000,000
Nicor Gas [Member] | Senior Notes And Pollution Control Bond [Member] | First Mortgage Bonds Due 2031 [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount																							100,000,000
Nicor Gas [Member] | Senior Notes And Pollution Control Bond [Member] | First Mortgage Bonds Due 2036 [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount																							$ 50,000,000
Parent Company [Member]
Financing (Textual) [Abstract]
Bank Loans																$ 400,000,000	400,000,000
Ratio of indebtedness to capitalization, debt covenant, required																70.00%				70.00%
Senior Notes outstanding																$ 10,300,000,000	2,400,000,000
Unused credit with banks																2,250,000,000
Expires, 2020																1,250,000,000
Line of Credit Facility, Maximum Borrowing Capacity																2,250,000,000
Line of Credit Expire Year One																0
Parent Company [Member] | Series 2011A [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation										1.95%
Parent Company [Member] | Unsecured Debt [Member] | Series 2011A [Member]
Financing (Textual) [Abstract]
Repayments of Senior Debt										$ 500,000,000
Parent Company [Member] | Junior Subordinated Debt [Member] | Senior Notes Due Two Thousand Seventy Six [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount										$ 800,000,000
Fixed stated interest rate of debt obligation										5.25%
Parent Company [Member] | Junior Subordinated Debt [Member] | Junior Subordinated Notes Due Two Thousand Fifty Seven [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount																$ 550,000,000
Fixed stated interest rate of debt obligation																5.50%				5.50%
Southern Natural Gas Company, LLC [Member] | Southern Company Gas [Member]
Debt Instrument [Line Items]
Ownership percentage, equity method investment																						50.00%
Notes due September 30, 2032 [Member] | Southern Power [Member]
Financing (Textual) [Abstract]
Promissory Note																$ 5,000,000
Capital Lease Obligations | Georgia Power [Member] | Secured Debt [Member]
Financing (Textual) [Abstract]
Long-term Debt																$ 169,000,000	183,000,000
5.20% Class A Preferred Stock [Member] | Alabama Power [Member]
Debt Instrument [Line Items]
Temporary Equity, Shares Outstanding | shares													6,480,000
Financing (Textual) [Abstract]
Temporary Equity, Dividend Rate Percentage													0.052			0.0520
Temporary Equity, Par or Stated Value Per Share | $ / shares													$ 25
5.20% Class A Preferred Stock [Member] | Alabama Power [Member] | Aggregate Stated Capital [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount													$ 162,000,000
5.30% Class A Preferred Stock [Member] | Alabama Power [Member]
Debt Instrument [Line Items]
Temporary Equity, Shares Outstanding | shares													4,000,000
Financing (Textual) [Abstract]
Temporary Equity, Dividend Rate Percentage													0.053			0.0530
5.30% Class A Preferred Stock [Member] | Alabama Power [Member] | Aggregate Stated Capital [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount													$ 100,000,000
5.625% Preference Stock [Member] | Alabama Power [Member]
Debt Instrument [Line Items]
Temporary Equity, Shares Outstanding | shares													6,000,000
Financing (Textual) [Abstract]
Temporary Equity, Dividend Rate Percentage													0.05625			0.05625
5.625% Preference Stock [Member] | Alabama Power [Member] | Aggregate Stated Capital [Member]
Financing (Textual) [Abstract]
Debt Instrument, Face Amount													$ 150,000,000
Commercial Paper [Member]
Financing (Textual) [Abstract]
Short Term Borrowings Excluding Other Energy Service Contracts																$ 1,909,000,000	740,000,000
Commercial Paper [Member] | Georgia Power [Member]
Financing (Textual) [Abstract]
Short Term Borrowings Excluding Other Energy Service Contracts																392,000,000	158,000,000
Commercial Paper [Member] | Mississippi Power [Member]
Financing (Textual) [Abstract]
Short Term Borrowings Excluding Other Energy Service Contracts																0	0
Commercial Paper [Member] | Gulf Power [Member]
Financing (Textual) [Abstract]
Short Term Borrowings Excluding Other Energy Service Contracts																168,000,000	142,000,000
Commercial Paper [Member] | Southern Power [Member]
Financing (Textual) [Abstract]
Short Term Borrowings Excluding Other Energy Service Contracts																0	0
Long-term Debt [Member] | Parent Company [Member]
Financing (Textual) [Abstract]
Bank Loans																2,000,000,000
Short-term Debt [Member] | Mississippi Power [Member]
Financing (Textual) [Abstract]
Bank loans outstanding																	475,000,000
Short-term Debt [Member] | Parent Company [Member]
Financing (Textual) [Abstract]
Bank Loans																100,000,000
Long-Term Debt And Capital Lease Obligations, Current [Member] | Mississippi Power [Member]
Financing (Textual) [Abstract]
Bank loans outstanding																	425,000,000
Power Purchase Agreement [Member] | Georgia Power [Member]
Financing (Textual) [Abstract]
Capital leased assets, gross																149,000,000	149,000,000
Capitalized lease obligations																$ 141,000,000	148,000,000
Capital Leased Assets, Number of Units | leased_asset_units																2				2
Accumulated depreciation PPE																$ 19,000,000	10,000,000
Power Purchase Agreement [Member] | Georgia Power [Member] | Minimum [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																10.00%				10.00%
Power Purchase Agreement [Member] | Georgia Power [Member] | Maximum [Member]
Financing (Textual) [Abstract]
Fixed stated interest rate of debt obligation																11.00%				11.00%
FFB Loan [Member] | Georgia Power [Member]
Financing (Textual) [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity																$ 2,600,000,000	2,200,000,000
Continuing Letter of Credit Facility [Member] | Southern Power [Member]
Financing (Textual) [Abstract]
Unused credit with banks																82,000,000
Line of Credit Facility, Maximum Borrowing Capacity																120,000,000
Construction Loan And Bridge Loan [Member] | Southern Power [Member]
Financing (Textual) [Abstract]
Line of Credit Facility, Current Borrowing Capacity																$ 209,000,000	$ 137,000,000
Debt, Weighted Average Interest Rate																2.10%	2.00%			2.10%
Southern Company Gas Capital [Member] | Southern Company Gas [Member]
Debt Instrument [Line Items]
Noncontrolling ownership percentage held by parent																	100.00%
Parent Company [Member] | Mississippi Power [Member]
Financing (Textual) [Abstract]
Promissory Note																$ 551,000,000	$ 576,000,000
Mankato [Member] | Southern Power [Member]
Debt Instrument [Line Items]
Noncontrolling ownership percentage held by parent			100.00%
Financing (Textual) [Abstract]
Life Output Of Plant			10 years													10 years
Mankato Expansion [Member] | Southern Power [Member]
Financing (Textual) [Abstract]
Life Output Of Plant																20 years
Senior Lien [Member] | Southern Power [Member]
Financing (Textual) [Abstract]
Assets																$ 408,000,000