Amount of variable rate pollution control revenue bonds outstanding requiring liquidity support.

No definition available.

Name:	so_AmountOfVariableRatePollutionControlRevenueBondsOutstandingRequiringLiquiditySupport
Namespace Prefix:	so_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of Fixed rate pollution control revenue bonds outstanding requiring liquidity support.

+ References

No definition available.

+ Details

Name:	so_AmountofFixedRatePollutionControlRevenueBondsOutstandingRequiringLiquiditySupport
Namespace Prefix:	so_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Expected Debt Issuance

+ References

No definition available.

+ Details

Name:	so_ExpectedDebtIssuance
Namespace Prefix:	so_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Expected Equity Issuance

+ References

No definition available.

+ Details

Name:	so_ExpectedEquityIssuance
Namespace Prefix:	so_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line of Credit Facility, Average Amount Outstanding

+ References

No definition available.

+ Details

Name:	so_LineofCreditFacilityAverageAmountOutstanding
Namespace Prefix:	so_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Promissory Note

+ References

No definition available.

+ Details

Name:	so_PromissoryNote
Namespace Prefix:	so_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Redemption Amount Of Principal Notes

+ References

No definition available.

+ Details

Name:	so_RedemptionAmountOfPrincipalNotes
Namespace Prefix:	so_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow for the extinguishment of long-term borrowing, with the highest claim on the assets of the entity in case of bankruptcy or liquidation, before its maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3291-108585

+ Details

Name:	us-gaap_EarlyRepaymentOfSeniorDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=so_BridgeAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_ScenarioPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=so_AlabamaPowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=so_SeriesFFMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=so_Series2016AMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_UnsecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=so_BankLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=so_GeorgiaPowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=so_Series2016BMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=so_Series2013BMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=so_GulfPowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=so_MississippiPowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_NotesPayableToBanksMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortTermDebtTypeAxis=so_ShortTermNoteRenewedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=so_TraditionalOperatingCompaniesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=us-gaap_ParentCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=so_SouthernPowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=so_DebtDueFebruaryTwentyEighthTwoThousandThirtySixMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=so_ProjectCreditFacilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Financing - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended
Financing - Narrative (Details) - USD ($)	Jan. 31, 2016	Mar. 31, 2016	Mar. 14, 2016	Mar. 08, 2016	Jan. 29, 2016	Jan. 19, 2016	Sep. 30, 2015
Debt Instrument [Line Items]
Amount of Variable Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support		$ 1,800,000,000
Maximum Borrowing Capacity		6,495,000,000
Remaining Borrowing Capacity		6,412,000,000
Bridge Agreement [Member]
Debt Instrument [Line Items]
Maximum Borrowing Capacity							$ 8,100,000,000
Scenario, Plan [Member] \| Bridge Agreement [Member]
Debt Instrument [Line Items]
Expected Debt Issuance (minimum)		8,000,000,000
Expected Equity Issuance (maximum)		1,200,000,000
Alabama Power [Member]
Debt Instrument [Line Items]
Amount of Variable Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support		810,000,000
Amount of Fixed Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support		167,000,000
Maximum Borrowing Capacity		1,340,000,000
Remaining Borrowing Capacity		1,340,000,000
Alabama Power [Member] \| Series FF [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.20%
Alabama Power [Member] \| Senior Notes [Member] \| Series 2016A [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 400,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.30%
Alabama Power [Member] \| Unsecured Debt [Member] \| Series FF [Member]
Debt Instrument [Line Items]
Redemption Amount Of Principal Notes	$ 200,000,000
Alabama Power [Member] \| Bank Loans [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 45,000,000
Debt Instrument, Interest Rate, Stated Percentage		2.38%
Georgia Power [Member]
Debt Instrument [Line Items]
Amount of Variable Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support		$ 868,000,000
Amount of Fixed Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support		69,000,000
Maximum Borrowing Capacity		1,750,000,000
Remaining Borrowing Capacity		1,732,000,000
Georgia Power [Member] \| Senior Notes [Member] \| Series 2016A [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 325,000,000
Debt Instrument, Interest Rate, Stated Percentage		3.25%
Georgia Power [Member] \| Senior Notes [Member] \| Series 2016B [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 325,000,000
Debt Instrument, Interest Rate, Stated Percentage		2.40%
Georgia Power [Member] \| Unsecured Debt [Member] \| Series 2013B [Member]
Debt Instrument [Line Items]
Redemption Amount Of Principal Notes		$ 250,000,000
Gulf Power [Member]
Debt Instrument [Line Items]
Amount of Variable Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support		82,000,000
Amount of Fixed Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support		33,000,000
Maximum Borrowing Capacity		280,000,000
Remaining Borrowing Capacity		280,000,000
Mississippi Power [Member]
Debt Instrument [Line Items]
Amount of Variable Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support		40,000,000
Maximum Borrowing Capacity		205,000,000
Line of Credit Facility, Current Borrowing Capacity		100,000,000	$ 50,000,000		$ 50,000,000	$ 100,000,000
Promissory Note	$ 275,000,000
Remaining Borrowing Capacity		180,000,000
Mississippi Power [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Redemption Amount Of Principal Notes				$ 300,000,000
Mississippi Power [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
Maximum Borrowing Capacity				1,200,000,000
Line of Credit Facility, Current Borrowing Capacity				900,000,000
Remaining Borrowing Capacity				300,000,000
Mississippi Power [Member] \| Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Redemption Amount Of Principal Notes				$ 900,000,000
Mississippi Power [Member] \| Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		10,000,000
Traditional Operating Companies [Member]
Debt Instrument [Line Items]
Amount of Fixed Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support		269,000,000
Southern Company [Member]
Debt Instrument [Line Items]
Maximum Borrowing Capacity		2,250,000,000
Remaining Borrowing Capacity		2,250,000,000
Southern Power [Member]
Debt Instrument [Line Items]
Maximum Borrowing Capacity		600,000,000
Line of Credit Facility, Current Borrowing Capacity		$ 276,000,000
Debt, Weighted Average Interest Rate		1.99%
Remaining Borrowing Capacity		$ 560,000,000
Early Repayment of Senior Debt		3,000,000
Southern Power [Member] \| TRE Debt Due 2036 [Member]
Debt Instrument [Line Items]
Promissory Note		2,000,000
Southern Power [Member] \| Project Credit Facilities [Member]
Debt Instrument [Line Items]
Maximum Borrowing Capacity		413,000,000
Line of Credit Facility, Current Borrowing Capacity		$ 413,000,000
Debt, Weighted Average Interest Rate		1.99%
Line of Credit Facility, Average Amount Outstanding		$ 260,000,000
Southern Power [Member] \| Letter of Credit [Member]
Debt Instrument [Line Items]
Maximum Borrowing Capacity		149,000,000
Line of Credit Facility, Current Borrowing Capacity		8,000,000
Remaining Borrowing Capacity		$ 74,000,000