STOCK COMPENSATION - Aggregate Intrinsic Value for Options Exercised (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate intrinsic value for options outstanding	$ 124
Aggregate intrinsic value for options exercisable	124
Intrinsic value of options exercised	167	$ 9	$ 64
Tax benefit of options exercised	35	2	25
Alabama Power
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate intrinsic value for options outstanding	14
Aggregate intrinsic value for options exercisable	14
Intrinsic value of options exercised	21	2	12
Tax benefit of options exercised	4	0	5
Georgia Power
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate intrinsic value for options outstanding	35
Aggregate intrinsic value for options exercisable	35
Intrinsic value of options exercised	30	2	13
Tax benefit of options exercised	6	0	5
Mississippi Power
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate intrinsic value for options outstanding	6
Aggregate intrinsic value for options exercisable	6
Intrinsic value of options exercised	4	1	2
Tax benefit of options exercised	$ 1	$ 0	$ 1

Amount of tax benefit from exercise of option under share-based payment arrangement.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

+ References

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-Publisher FASB
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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

+ References

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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