Nuclear Insurance (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Apr. 30, 2014	Dec. 31, 2016
Jointly Owned Utility Plant Interests [Line Items]
Maximum fund for public liability claims arising from a single nuclear incident under Price-Anderson Amendments Act		$ 13,400
Maximum insurance coverage provided by American Nuclear Insurers to each nuclear plant		375
Maximum amount that a company could be assessed per incident for each licensed reactor		127
Maximum aggregate amount that a reactor can assess in a calendar period for each incident		$ 19
Block period considered for inflation adjustment against maximum assessment per reactor		5 years
Maximum deductible waiting period		26 weeks
Maximum coverage per occurrence per unit limit to obtain replacement power		$ 490
Approximate period over which maximum per occurrence per unit limit is exhausted		3 years
Aggregate payment for claims resulting from terrorist acts in one year period		$ 3,200
Vogtle Units 3 and 4 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Maximum limits for accidental property damage occurring during construction		2,750
Alabama Power [Member]
Jointly Owned Utility Plant Interests [Line Items]
Maximum fund for public liability claims arising from a single nuclear incident under Price-Anderson Amendments Act		13,400
Maximum insurance coverage provided by American Nuclear Insurers to each nuclear plant		375
Maximum amount that a company could be assessed per incident for each licensed reactor		127
Maximum aggregate amount that a reactor can assess in a calendar period for each incident		19
Maximum assessment, excluding any applicable state premium taxes		255
Maximum aggregate amount to be paid in one year		$ 38
Block period considered for inflation adjustment against maximum assessment per reactor		5 years
Maximum property damage insurance provided to nuclear generating facilities		$ 1,500
Maximum additional coverage provided for losses under excess insurance		1,250
Maximum Sublimit Non-Nuclear Losses		$ 750
Maximum deductible waiting period		26 weeks
Maximum Deductible Waiting Period Days		182 days
Maximum coverage per occurrence per unit limit to obtain replacement power		$ 490
Current maximum annual assessments under NEIL policies		53
Aggregate payment for claims resulting from terrorist acts in one year period		$ 3,200
Elected Deductible Waiting Period, Days		84 days
Georgia Power [Member]
Jointly Owned Utility Plant Interests [Line Items]
Maximum fund for public liability claims arising from a single nuclear incident under Price-Anderson Amendments Act		$ 13,400
Maximum insurance coverage provided by American Nuclear Insurers to each nuclear plant		375
Maximum amount that a company could be assessed per incident for each licensed reactor		127
Maximum aggregate amount that a reactor can assess in a calendar period for each incident		19
Maximum assessment, excluding any applicable state premium taxes		247
Maximum aggregate amount to be paid in one year		$ 37
Block period considered for inflation adjustment against maximum assessment per reactor		5 years
Block period considered for inflation adjustment against maximum yearly assessment		5 years
Maximum property damage insurance provided to nuclear generating facilities		$ 1,500
Maximum additional coverage provided for losses under excess insurance		1,250
Maximum Sublimit Non-Nuclear Losses		$ 750
Maximum deductible waiting period		26 weeks
Maximum coverage per occurrence per unit limit to obtain replacement power		$ 490
Approximate period over which maximum per occurrence per unit limit is exhausted		3 years
Elected deductible waiting period		12-week
Current maximum annual assessments under NEIL policies		$ 82
Aggregate payment for claims resulting from terrorist acts in one year period		3,200
Georgia Power [Member] | Vogtle Units 3 and 4 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Maximum limits for accidental property damage occurring during construction		2,750
Alabama Power and Georgia Power [Member]
Jointly Owned Utility Plant Interests [Line Items]
Maximum property damage insurance provided to nuclear generating facilities		1,500
Maximum additional coverage provided for losses under excess insurance	$ 750	$ 1,250
Elected deductible waiting period		12-week