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LEASES - Lease Costs (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Lease cost |  |  |
Operating lease cost | $ 313 | $ 309 | $ 310
Finance lease cost: |  |  |
Amortization of ROU assets | 21 | 26 | 28
Interest on lease obligations | 11 | 11 | 12
Total finance lease cost | 32 | 37 | 40
Short-term lease costs | 48 | 39 | 48
Variable lease cost | 96 | 91 | 105
Sublease income | 1 | 0 | 0
Total lease cost | 490 | 476 | 503
Assets Subject to Power Purchase Agreement |  |  |
Lease cost |  |  |
Operating lease cost | 165 | 161 | 149
Alabama Power |  |  |
Lease cost |  |  |
Operating lease cost | 58 | 55 | 54
Finance lease cost: |  |  |
Amortization of ROU assets | 1 | 1 | 1
Interest on lease obligations | 0 | 0 | 0
Total finance lease cost | 1 | 1 | 1
Short-term lease costs | 15 | 11 | 19
Variable lease cost | 4 | 4 | 6
Sublease income | 0 | (1) | (1)
Total lease cost | 78 | 70 | 79
Alabama Power | Assets Subject to Power Purchase Agreement |  |  |
Lease cost |  |  |
Operating lease cost | 47 | 43 | 41
Georgia Power |  |  |
Lease cost |  |  |
Operating lease cost | 208 | 212 | 206
Finance lease cost: |  |  |
Amortization of ROU assets | 11 | 15 | 15
Interest on lease obligations | 16 | 16 | 18
Total finance lease cost | 27 | 31 | 33
Short-term lease costs | 24 | 26 | 22
Variable lease cost | 83 | 76 | 85
Sublease income | 0 | 0 | 0
Total lease cost | 342 | 345 | 346
Georgia Power | Assets Subject to Power Purchase Agreement |  |  |
Lease cost |  |  |
Operating lease cost | 184 | 184 | 174
Mississippi Power |  |  |
Lease cost |  |  |
Operating lease cost | 2 | 3 | 3
Finance lease cost: |  |  |
Amortization of ROU assets | 1 | 0 | 0
Interest on lease obligations | 1 | 0 | 0
Total finance lease cost | 2 | 0 | 0
Short-term lease costs | 0 | 0 | 0
Variable lease cost | 0 | 0 | 0
Sublease income | 0 | 0 | 0
Total lease cost | 4 | 3 | 3
Southern Power |  |  |
Lease cost |  |  |
Operating lease cost | 33 | 29 | 28
Finance lease cost: |  |  |
Amortization of ROU assets | 0 | 0 | 0
Interest on lease obligations | 0 | 0 | 0
Total finance lease cost | 0 | 0 | 0
Short-term lease costs | 0 | 0 | 0
Variable lease cost | 5 | 7 | 7
Sublease income | 0 | 0 | 0
Total lease cost | 38 | 36 | 35
Southern Company Gas |  |  |
Lease cost |  |  |
Operating lease cost | 19 | 19 | 18
Finance lease cost: |  |  |
Amortization of ROU assets | 0 | 0 | 0
Interest on lease obligations | 0 | 0 | 0
Total finance lease cost | 0 | 0 | 0
Short-term lease costs | 0 | 0 | 0
Variable lease cost | 0 | 0 | 0
Sublease income | 0 | 0 | 0
Total lease cost | $ 19 | $ 19 | $ 18

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- Definition Amount of interest expense on finance lease liability. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918686-209980 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123391704&loc=SL77918638-209977 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 55 -Paragraph 53 -URI http://asc.fasb.org/extlink&oid=123414884&loc=SL77918982-209971 + Details
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- Definition Amount of amortization expense attributable to right-of-use asset from finance lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918686-209980 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123391704&loc=SL77918638-209977 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 55 -Paragraph 53 -URI http://asc.fasb.org/extlink&oid=123414884&loc=SL77918982-209971 + Details
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- Definition Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 55 -Paragraph 53 -URI http://asc.fasb.org/extlink&oid=123414884&loc=SL77918982-209971 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918686-209980 + Details
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