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ASSET RETIREMENT OBLIGATIONS - Investment Securities in the Funds (Details) - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020
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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

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