ASSET RETIREMENT OBLIGATIONS - Investment Securities in the Funds (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Marketable Securities [Line Items]
Total investment securities in the Funds	$ 2,541	$ 2,301
Equity securities
Marketable Securities [Line Items]
Total investment securities in the Funds	1,358	1,339
Debt securities
Marketable Securities [Line Items]
Total investment securities in the Funds	986	851
Other securities
Marketable Securities [Line Items]
Total investment securities in the Funds	197	111
Alabama Power
Marketable Securities [Line Items]
Total investment securities in the Funds	1,324	1,156
Alabama Power | Equity securities
Marketable Securities [Line Items]
Total investment securities in the Funds	849	842
Alabama Power | Debt securities
Marketable Securities [Line Items]
Total investment securities in the Funds	316	231
Alabama Power | Other securities
Marketable Securities [Line Items]
Total investment securities in the Funds	159	83
Georgia Power
Marketable Securities [Line Items]
Total investment securities in the Funds	1,217	1,145
Georgia Power | Equity securities
Marketable Securities [Line Items]
Total investment securities in the Funds	509	497
Georgia Power | Debt securities
Marketable Securities [Line Items]
Total investment securities in the Funds	670	620
Georgia Power | Other securities
Marketable Securities [Line Items]
Total investment securities in the Funds	$ 38	$ 28