Regulatory Matters - Nuclear Construction (Details) - GEORGIA POWER CO $ in Millions						1 Months Ended		3 Months Ended	12 Months Ended			36 Months Ended
	Jan. 01, 2021	Jan. 01, 2020	Feb. 19, 2019 USD ($)	Jan. 11, 2018 USD ($)	Jan. 01, 2016	Dec. 31, 2018 USD ($) appeal	Aug. 31, 2018 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2009 USD ($) utility MW	Dec. 31, 2022 USD ($)	Dec. 31, 2014	Dec. 31, 2013
Loss Contingencies [Line Items]
Number of construction units approved | utility											2
Electric generating capacity in mega watts under consortium agreement | MW											1,100
Additional construction capital costs				$ 3,300.0
Estimated in-service capital cost											$ 4,418.0
Financing costs collected, net of tax								$ 1,900.0
Increase in NCCR tariff						$ 88.0
Amendment to estimated in-service capital cost				$ 5,680.0
Retail rate of return on common equity														10.95%
Number of appeals | appeal						2
Requested capital construction costs			$ 5,400.0
Deferred approval of expenditures related to administrative claim			$ 51.6
FFB Loan
Loss Contingencies [Line Items]
Long-term line of credit								3,460.0
Eligible project costs to be reimbursed								$ 5,130.0
Plant Vogtle Units 3 And 4
Loss Contingencies [Line Items]
Proportionate ownership share								45.70%
Construction financing costs								$ 1,900.0
Base project capital cost forecast, monthly								50.0
Monthly AFUDC								12.0
Percentage of ownership interest required for voting for continuing construction							90.00%						90.00%
Cost settlement agreement revised forecast, net of payments								$ 7,300.0
Public utilities, approved return on equity percentage					10.00%
Public utilities, approved return on equity, monthly percentage decrease								0.10%
Return on equity reduction, negative impact on earnings										$ 100.0
Requested capital construction costs							$ 578.0
Guarantor obligations								$ 1,700.0
Customer refund								$ 188.0
Plant Vogtle Units 3 And 4 | Scenario, Forecast
Loss Contingencies [Line Items]
Construction financing costs									$ 3,100.0
Public utilities, approved return on equity percentage	5.30%	8.30%
Return on equity reduction, negative impact on earnings									$ 75.0			$ 635.0
Plant Vogtle Units 3 And 4 | Vogtle Owners
Loss Contingencies [Line Items]
Period of notice required in the event letters of credit are not renewed								30 days