Nuclear Insurance (Details)	12 Months Ended
	Dec. 31, 2017 USD ($)
Jointly Owned Utility Plant Interests [Line Items]
Maximum fund for public liability claims arising from a single nuclear incident under price-anderson amendments act	$ 13,400,000,000
Maximum insurance coverage provided by American Nuclear Insurers to each nuclear plant	450,000,000
Maximum amount that a company could be assessed per incident for each licensed reactor	127,000,000
Maximum aggregate amount that a reactor can assess in a calendar period for each incident	$ 19,000,000
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	$ 490,000,000
Aggregate payment for claims resulting from terrorist acts in one year period	3,200,000,000
Vogtle Units 3 and 4
Jointly Owned Utility Plant Interests [Line Items]
Maximum limits for accidental property damage occurring during construction	2,750,000,000
ALABAMA POWER CO
Jointly Owned Utility Plant Interests [Line Items]
Maximum fund for public liability claims arising from a single nuclear incident under price-anderson amendments act	13,400,000,000
Maximum insurance coverage provided by American Nuclear Insurers to each nuclear plant	450,000,000
Maximum amount that a company could be assessed per incident for each licensed reactor	127,000,000
Maximum aggregate amount that a reactor can assess in a calendar period for each incident	19,000,000
Maximum assessment, excluding any applicable state premium taxes	255,000,000
Maximum aggregate amount to be paid in one year	$ 38,000,000
Block period considered for inflation adjustment against maximum assessment per reactor	5 years
Maximum property damage insurance provided to nuclear generating facilities	$ 1,500,000,000
Maximum additional coverage provided for losses under excess insurance	$ 1,250,000,000
Maximum deductible waiting period	26 weeks
Maximum coverage per occurrence per unit limit to obtain replacement power	$ 490,000,000
Current maximum annual assessments under NEIL policies	55,000,000
Aggregate payment for claims resulting from terrorist acts in one year period	$ 3,200,000,000
Elected deductible waiting period, days	84 days
Maximum sublimit non-nuclear losses	$ 750,000,000
Maximum deductible waiting period days	182 days
GEORGIA POWER CO
Jointly Owned Utility Plant Interests [Line Items]
Maximum fund for public liability claims arising from a single nuclear incident under price-anderson amendments act	$ 13,400,000,000
Maximum insurance coverage provided by American Nuclear Insurers to each nuclear plant	450,000,000
Maximum amount that a company could be assessed per incident for each licensed reactor	127,000,000
Maximum aggregate amount that a reactor can assess in a calendar period for each incident	19,000,000
Maximum assessment, excluding any applicable state premium taxes	247,000,000
Maximum aggregate amount to be paid in one year	$ 37,000,000
Block period considered for inflation adjustment against maximum assessment per reactor	5 years
Maximum property damage insurance provided to nuclear generating facilities	$ 1,500,000,000
Maximum additional coverage provided for losses under excess insurance	$ 1,250,000,000
Maximum deductible waiting period	26 weeks
Maximum coverage per occurrence per unit limit to obtain replacement power	$ 490,000,000
Elected deductible waiting period	12-week
Current maximum annual assessments under NEIL policies	$ 81,000,000
Aggregate payment for claims resulting from terrorist acts in one year period	$ 3,200,000,000
Block period considered for inflation adjustment against maximum yearly assessment	5 years
Maximum sublimit non-nuclear losses	$ 750,000,000
GEORGIA POWER CO | Vogtle Units 3 and 4
Jointly Owned Utility Plant Interests [Line Items]
Maximum limits for accidental property damage occurring during construction	2,750,000,000
Alabama Power and Georgia Power
Jointly Owned Utility Plant Interests [Line Items]
Maximum property damage insurance provided to nuclear generating facilities	1,500,000,000
Maximum additional coverage provided for losses under excess insurance	1,250,000,000
Maximum Additional Coverage Provided For Losses Under Excess Insurance, Non-Nuclear Losses	$ 750,000,000
Elected deductible waiting period	12-week