Regulatory Matters - Nuclear Construction DOE Financing (Details) - USD ($)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2017
Loss Contingencies [Line Items]
Line of credit facility, maximum borrowing capacity		$ 7,863,000,000
Georgia Power
Loss Contingencies [Line Items]
Line of credit facility, maximum borrowing capacity		1,750,000,000
Eligible project costs to be reimbursed	$ 3,460,000,000
Georgia Power | Loan Guarantee Agreement
Loss Contingencies [Line Items]
Credit facility conditional borrowing commitment				$ 1,670,000,000
Georgia Power | FFB Loan
Loss Contingencies [Line Items]
Line of credit facility, maximum borrowing capacity		$ 2,625,000,000.000	$ 2,600,000,000.0