CONTINGENCIES, COMMITMENTS, AND GUARANTEES - Nuclear Fuel Disposal Costs and Nuclear Insurance (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) plant
Jointly Owned Utility Plant Interests [Line Items]
Maximum fund for public liability claims arising from a single nuclear incident under price-anderson amendments act	$ 13,900,000,000
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	138,000,000
Maximum aggregate amount that a reactor can assess in a calendar period for each incident	$ 20,000,000
Block period considered for inflation adjustment against maximum assessment per reactor	5 years
Maximum deductible waiting period	182 days
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
Jointly Owned Utility Plant Interests [Line Items]
Maximum assessment, excluding any applicable state premium taxes	275,000,000
Maximum aggregate amount to be paid in one year	41,000,000
Current maximum annual assessments under NEIL policies	58,000,000
Georgia Power
Jointly Owned Utility Plant Interests [Line Items]
Maximum assessment, excluding any applicable state premium taxes	267,000,000
Maximum aggregate amount to be paid in one year	40,000,000
Current maximum annual assessments under NEIL policies	$ 85,000,000
Alabama Power and Georgia Power
Jointly Owned Utility Plant Interests [Line Items]
Number of nuclear fuel plants | plant	3
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