Contingencies and Regulatory Matters - Revised Cost and Schedule - Georgia Power (Details) - USD ($) $ in Millions	9 Months Ended	105 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Construction work in progress	$ 8,026	$ 8,026	$ 8,977
GEORGIA POWER CO
Loss Contingencies [Line Items]
Construction work in progress	5,751	5,751	$ 4,939
Financing costs incurred		1,500
Financing costs collected, net of tax	1,500
Estimated cancellation costs		350
GEORGIA POWER CO | Minimum
Loss Contingencies [Line Items]
Estimated financing costs		3,400
Cancellation Decision | GEORGIA POWER CO
Loss Contingencies [Line Items]
Construction work in progress	4,600	4,600
Guarantee Obligations	(1,700)	(1,700)
Financing costs collected, net of tax		1,500
Estimated cancellation costs		400
Estimated net cancellation cost	4,800	4,800
Plant Vogtle Units 3 And 4 | GEORGIA POWER CO
Loss Contingencies [Line Items]
Estimated cost to complete	4,200	4,200
Construction work in progress	4,600	4,600
Guarantee Obligations	(1,700)	(1,700)
Estimated capital costs	7,100	7,100
Vogtle Cost Settlement Agreement Revised Forecast	(5,700)	(5,700)
Estimated net additional capital costs	$ 1,400	$ 1,400