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

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

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Eligible Project Costs To Be Reimbursed

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Funds Received Under Guarantee Settlement Agreement, Less Customer Refunds

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Line Of Credit Facility, Percent Of Eligible Project Costs To Be Reimbursed

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Number Of Short-Term Loans

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Number of Term Loan Facilities

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Ownership Interest Percentage Required for Voting for Continuing Construction

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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

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

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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.

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Fair value amount of debt instrument that was repurchased.

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Face (par) amount of the original debt instrument that was repurchased.

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The proportionate share of interest (percent) in a jointly owned utility plant.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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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.

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Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

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The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

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The cash outflow for a borrowing having initial term of repayment within one year or the normal operating cycle, if longer.

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Financing - Narrative (Details)	1 Months Ended				3 Months Ended		6 Months Ended		12 Months Ended
Financing - Narrative (Details)	Jun. 30, 2019 USD ($) loan	May 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Jan. 31, 2019 USD ($)	Jun. 30, 2019 USD ($) shares	Jun. 30, 2018 shares	Jun. 30, 2019 USD ($) loan shares	Jun. 30, 2018 USD ($) shares	Dec. 31, 2014	Apr. 30, 2019 USD ($)	Aug. 31, 2018
Debt Instrument [Line Items]
Variable rate pollution control revenue bonds outstanding	$ 1,400,000,000				$ 1,400,000,000		$ 1,400,000,000
Fixed rate pollution control revenue bonds outstanding	272,000,000				272,000,000		272,000,000
Borrowing capacity	7,583,000,000				$ 7,583,000,000		7,583,000,000
Repayments of short-term debt							$ 1,850,000,000	$ 550,000,000
Stock-based compensation awards not included in the diluted earnings per share calculation because they were anti-dilutive (in shares) \| shares					0	5,300,000	0	0
Senior Notes
Debt Instrument [Line Items]
Repayments of debt				$ 1,200,000,000
Senior Notes \| 1.85% Notes
Debt Instrument [Line Items]
Interest rate				1.85%
Repurchase amount				$ 522,000,000
Debt face amount				$ 1,000,000,000.0
Senior Notes \| Series 2014B Notes
Debt Instrument [Line Items]
Interest rate				2.15%
Repurchase amount				$ 180,000,000
Debt face amount				350,000,000
Senior Notes \| Series 2018A Notes
Debt Instrument [Line Items]
Repurchase amount				504,000,000
Debt face amount				750,000,000
Notes Payable to Banks \| Uncommitted Bank Credit Arrangement
Debt Instrument [Line Items]
Repayments of short-term debt				250,000,000
Notes Payable to Banks \| Floating Rate Bank Term Loan Agreement
Debt Instrument [Line Items]
Repayments of short-term debt				1,500,000,000
ALABAMA POWER CO
Debt Instrument [Line Items]
Variable rate pollution control revenue bonds outstanding	854,000,000				$ 854,000,000		$ 854,000,000
Fixed rate pollution control revenue bonds outstanding	87,000,000				87,000,000		87,000,000
Borrowing capacity	1,303,000,000				1,303,000,000		1,303,000,000
GEORGIA POWER CO
Debt Instrument [Line Items]
Variable rate pollution control revenue bonds outstanding	550,000,000				550,000,000		550,000,000
Fixed rate pollution control revenue bonds outstanding	185,000,000				185,000,000		185,000,000
Borrowing capacity	1,750,000,000				1,750,000,000		1,750,000,000
Repayments of short-term debt							0	$ 150,000,000
GEORGIA POWER CO \| Municipal bonds \| Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project) First Series 1992
Debt Instrument [Line Items]
Redeemed aggregate principal amount				13,000,000
GEORGIA POWER CO \| Municipal bonds \| Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Eighth Series 1994
Debt Instrument [Line Items]
Redeemed aggregate principal amount				20,000,000
GEORGIA POWER CO \| Municipal bonds \| Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Second Series 1995
Debt Instrument [Line Items]
Redeemed aggregate principal amount				$ 75,000,000
GEORGIA POWER CO \| Municipal bonds \| Development Authority of Bartow County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Bowen Project), First Series 2009
Debt Instrument [Line Items]
Debt face amount			$ 173,000,000
GEORGIA POWER CO \| Municipal bonds \| Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), First Series 2013
Debt Instrument [Line Items]
Debt face amount			105,000,000
GEORGIA POWER CO \| Municipal bonds \| Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Second Series 2008
Debt Instrument [Line Items]
Debt face amount			65,000,000
GEORGIA POWER CO \| Municipal bonds \| Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Fourth Series 1994
Debt Instrument [Line Items]
Debt face amount										$ 55,000,000
GEORGIA POWER CO \| Municipal bonds \| Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Fourth Series 1995
Debt Instrument [Line Items]
Debt face amount										30,000,000
GEORGIA POWER CO \| Municipal bonds \| Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Ninth Series 1994
Debt Instrument [Line Items]
Debt face amount										20,000,000
GEORGIA POWER CO \| Municipal bonds \| Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Second Series 1994
Debt Instrument [Line Items]
Debt face amount										10,000,000
GEORGIA POWER CO \| Municipal bonds \| Development Authority of Burke County (Georgia) Pollution Control Revenue Bonds (Georgia Power Company Plant Vogtle Project), Fifth Series 1994
Debt Instrument [Line Items]
Debt face amount	$ 55,000,000				55,000,000		55,000,000
GEORGIA POWER CO \| Plant Vogtle Units 3 And 4
Debt Instrument [Line Items]
Undivided ownership interest									45.70%
GEORGIA POWER CO \| Notes Payable to Banks
Debt Instrument [Line Items]
Number of short-term loans \| loan	2
GEORGIA POWER CO \| Notes Payable to Banks \| First Short-Term Floating Rate Bank Loan
Debt Instrument [Line Items]
Debt face amount	$ 125,000,000				125,000,000		125,000,000
GEORGIA POWER CO \| Notes Payable to Banks \| Second Short-Term Floating Rate Bank Loan
Debt Instrument [Line Items]
Debt face amount	125,000,000				125,000,000		$ 125,000,000
GEORGIA POWER CO \| Term Loan
Debt Instrument [Line Items]
Number of term loan facilities \| loan							2
GEORGIA POWER CO \| 2014 FFB Credit Facility
Debt Instrument [Line Items]
Eligible project costs to be reimbursed							$ 5,130,000,000
Eligible project costs to be reimbursed, percentage									70.00%
Borrowings made			$ 835,000,000
Interest rate			3.213%
Borrowings outstanding	3,460,000,000				3,460,000,000		3,460,000,000
Amortization period for line of credit facility									5 years
GEORGIA POWER CO \| 2014 FFB Credit Facility \| U.S. Treasury Rate
Debt Instrument [Line Items]
Basis spread									0.375%
GEORGIA POWER CO \| Additional FFB Credit Facility
Debt Instrument [Line Items]
Eligible project costs to be reimbursed, percentage			70.00%
Amounts received under Guarantee Settlement Agreement, less Customer Refunds			$ 1,492,000,000
MISSISSIPPI POWER CO
Debt Instrument [Line Items]
Variable rate pollution control revenue bonds outstanding	40,000,000				40,000,000		40,000,000
Borrowing capacity	150,000,000				150,000,000		150,000,000
Repayments of short-term debt							0	200,000,000
MISSISSIPPI POWER CO \| Municipal bonds \| Mississippi Business Finance Corporation Pollution Control Revenue Refunding Bonds, Series 2002
Debt Instrument [Line Items]
Debt face amount			$ 43,000,000
MISSISSIPPI POWER CO \| Credit Arrangement
Debt Instrument [Line Items]
Borrowing capacity	50,000,000				50,000,000		50,000,000
SOUTHERN Co GAS
Debt Instrument [Line Items]
Borrowing capacity	1,750,000,000				1,750,000,000		1,750,000,000
SOUTHERN POWER CO
Debt Instrument [Line Items]
Borrowing capacity	600,000,000	$ 600,000,000			600,000,000		600,000,000			750,000,000
Repayments of short-term debt							100,000,000	$ 0
SOUTHERN POWER CO \| Notes Payable to Banks
Debt Instrument [Line Items]
Repayments of short-term debt		100,000,000
Southern Company Gas Capital
Debt Instrument [Line Items]
Borrowing capacity	1,250,000,000	$ 1,750,000,000			1,250,000,000		1,250,000,000			$ 1,900,000,000
Nicor Gas
Debt Instrument [Line Items]
Borrowing capacity	$ 500,000,000				$ 500,000,000		$ 500,000,000
Plant Vogtle Units 3 And 4 \| GEORGIA POWER CO
Debt Instrument [Line Items]
Undivided ownership interest	45.70%				45.70%		45.70%
Failure to vote, percentage of ownership interests									90.00%		90.00%