STOCK COMPENSATION - Schedule of Employees Participating in Stock-Based Compensation Programs (Details)	Dec. 31, 2019 employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of employees	2,320
Alabama Power
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of employees	307
Georgia Power
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of employees	370
Mississippi Power
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of employees	89
Southern Power
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of employees	50
Southern Company Gas
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of employees	285