PROPERTY, PLANT, AND EQUIPMENT - Property, Plant and Equipment (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Electric utilities:
Generation	$ 53,803	$ 52,179
Transmission	13,406	12,879
Distribution	22,236	20,958
General/other	5,423	5,072
Electric utilities' plant in service	94,868	91,088
Southern Company Gas:
Natural gas distribution utilities transportation and distribution	15,714	14,610
Storage facilities	1,315	1,752
Other	1,851	1,249
Southern Company Gas plant in service	18,880	17,611
Other plant in service	1,844	1,817
Total plant in service	115,592	110,516
Alabama Power
Electric utilities:
Generation	16,631	16,201
Transmission	5,334	5,033
Distribution	8,643	8,248
General/other	2,527	2,334
Electric utilities' plant in service	33,135	31,816
Southern Company Gas:
Natural gas distribution utilities transportation and distribution	0	0
Storage facilities	0	0
Other	0	0
Southern Company Gas plant in service	0	0
Other plant in service	0	0
Total plant in service	33,135	31,816
Georgia Power
Electric utilities:
Generation	19,184	18,675
Transmission	7,132	6,951
Distribution	12,437	11,622
General/other	2,579	2,434
Electric utilities' plant in service	41,332	39,682
Southern Company Gas:
Natural gas distribution utilities transportation and distribution	0	0
Storage facilities	0	0
Other	0	0
Southern Company Gas plant in service	0	0
Other plant in service	0	0
Total plant in service	41,332	39,682
Mississippi Power
Electric utilities:
Generation	2,791	2,819
Transmission	900	856
Distribution	1,156	1,088
General/other	259	248
Electric utilities' plant in service	5,106	5,011
Southern Company Gas:
Natural gas distribution utilities transportation and distribution	0	0
Storage facilities	0	0
Other	0	0
Southern Company Gas plant in service	0	0
Other plant in service	0	0
Total plant in service	5,106	5,011
Southern Power
Electric utilities:
Generation	14,551	13,872
Transmission	0	0
Distribution	0	0
General/other	34	32
Electric utilities' plant in service	14,585	13,904
Southern Company Gas:
Natural gas distribution utilities transportation and distribution	0	0
Storage facilities	0	0
Other	0	0
Southern Company Gas plant in service	0	0
Other plant in service	0	0
Total plant in service	14,585	13,904
Southern Company Gas
Electric utilities:
Generation	0	0
Transmission	0	0
Distribution	0	0
General/other	0	0
Electric utilities' plant in service	0	0
Southern Company Gas:
Natural gas distribution utilities transportation and distribution	15,714	14,610
Storage facilities	1,315	1,752
Other	1,851	1,249
Southern Company Gas plant in service	18,880	17,611
Other plant in service	0	0
Total plant in service	$ 18,880	$ 17,611