Contingencies and Regulatory Matters - Revised Cost and Schedule - Georgia Power (Details) - USD ($) $ in Millions	6 Months Ended	102 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Construction work in progress	$ 7,440.0	$ 7,440.0	$ 8,977.0
GEORGIA POWER CO
Loss Contingencies [Line Items]
Construction work in progress	5,422.0	5,422.0	$ 4,939.0
Financing costs incurred		1,400.0
Financing costs collected, net of tax	1,400.0
Estimated cancellation costs		400.0
GEORGIA POWER CO | Minimum
Loss Contingencies [Line Items]
Preliminary estimated cost to complete	3,900.0	3,900.0
Construction work in progress	4,480.0	4,480.0
Guarantee Obligations	(1,680.0)	(1,680.0)
Estimated capital costs	6,700.0	6,700.0
Vogtle Cost Settlement Agreement Revised Forecast	(5,680.0)	(5,680.0)
Estimated net additional capital costs	1,020.0	1,020.0
Estimated financing costs		3,100.0
GEORGIA POWER CO | Maximum
Loss Contingencies [Line Items]
Preliminary estimated cost to complete	4,600.0	4,600.0
Construction work in progress	4,480.0	4,480.0
Guarantee Obligations	(1,680.0)	(1,680.0)
Estimated capital costs	7,400.0	7,400.0
Vogtle Cost Settlement Agreement Revised Forecast	(5,680.0)	(5,680.0)
Estimated net additional capital costs	1,720.0	1,720.0
Estimated financing costs		3,500.0
Cancellation Decision | GEORGIA POWER CO
Loss Contingencies [Line Items]
Construction work in progress	4,500.0	4,500.0
Financing costs collected, net of tax		1,400.0
Estimated cancellation costs		400.0
Total	$ 6,300.0	$ 6,300.0