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SEGMENT AND RELATED INFORMATION - Financial Data for Business Segments (Details) $ in Millions |  |  | 1 Months Ended | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | --- | ---
Dec. 13, 2021 project | Jul. 01, 2021 USD ($) | Jan. 31, 2020 USD ($) | Jan. 31, 2019 USD ($) | Dec. 31, 2021 USD ($) | Sep. 30, 2021 USD ($) | Jun. 30, 2021 USD ($) | Mar. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Jun. 30, 2020 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2021 USD ($) project | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 23,113 | $ 20,375 | $ 21,419
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  |  |  |  | 3,565 | 3,518 | 3,038
Interest income |  |  |  |  |  |  |  |  |  |  |  |  |  | 22 | 37 | 60
Operating income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 3,698 | 4,885 | 7,736
Earnings from equity method investments |  |  |  |  |  |  |  |  |  |  |  |  |  | 76 | 153 | 162
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,837 | 1,821 | 1,736
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | 267 | 393 | 1,798
Segment net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,393 | 3,119 | 4,739
Goodwill |  |  |  |  | $ 5,280 |  |  |  | $ 5,280 |  | $ 5,280 | $ 5,280 | $ 5,280 | 5,280 | 5,280 | 5,280
Assets held for sale |  |  |  |  | 42 |  |  |  | 60 |  | 789 | 42 | 42 | 42 | 60 | 789
Total assets |  |  |  |  | 127,534 |  |  |  | 122,935 |  | 118,700 | 127,534 | 127,534 | 127,534 | 122,935 | 118,700
Segment and Related Information (Textual) [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated loss on Plant Vogtle Units 3 and 4 |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,692 |  | 0
Gain (loss) on dispositions |  |  |  |  |  |  |  |  |  |  |  |  |  | 176 | 66 | 2,588
Impairment charges |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 | 0 | 168
Gain (loss) on termination of leveraged leases |  |  |  |  |  |  |  |  |  |  |  |  |  | 93 |  |
Gain (loss) on termination of leveraged leases, after tax |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 99 |  |
Number of international projects subject to leveraged lease terminated | project | 2 |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |
Lease, impairment loss |  |  |  |  |  |  |  |  |  | $ 154 | 17 |  |  | $ 7 | 206 | 0
Lease, impairment loss, after tax |  |  |  |  |  |  |  |  |  | $ 74 | 13 |  |  |  |  |
Electric Utilities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | 18,300 | 16,497 | 17,095
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,953 | 2,941 | 2,472
Interest income |  |  |  |  |  |  |  |  |  |  |  |  |  | 21 | 30 | 47
Earnings from equity method investments |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 | 0 | 5
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 968 | 976 | 987
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | 219 | 517 | 708
Segment net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,247 | 3,115 | 3,268
Goodwill |  |  |  |  | 2 |  |  |  | 2 |  | 2 | 2 | 2 | 2 | 2 | 2
Assets held for sale |  |  |  |  | 39 |  |  |  | 5 |  | 618 | 39 | 39 | 39 | 5 | 618
Total assets |  |  |  |  | 101,774 |  |  |  | 98,041 |  | 94,650 | 101,774 | 101,774 | 101,774 | 98,041 | 94,650
Southern Company Gas |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | 4,380 | 3,434 | 3,792
All Other |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment and Related Information (Textual) [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Lease, impairment loss |  |  |  |  |  |  | $ 7 |  | 18 |  |  |  |  |  | 206 |
Lease, impairment loss, after tax |  |  |  |  |  |  | 6 |  | 14 |  |  |  |  |  | 105 |
Operating Segments | Traditional Electric Operating Companies | Electric Utilities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | 16,614 | 15,135 | 15,569
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,436 | 2,447 | 1,993
Interest income |  |  |  |  |  |  |  |  |  |  |  |  |  | 20 | 26 | 38
Earnings from equity method investments |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 | 0 | 2
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 821 | 825 | 818
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | 232 | 514 | 764
Segment net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,981 | 2,877 | 2,929
Goodwill |  |  |  |  | 0 |  |  |  | 0 |  | 0 | 0 | 0 | 0 | 0 | 0
Assets held for sale |  |  |  |  | 39 |  |  |  | 5 |  | 0 | 39 | 39 | 39 | 5 | 0
Total assets |  |  |  |  | 89,051 |  |  |  | 85,486 |  | 81,063 | 89,051 | 89,051 | 89,051 | 85,486 | 81,063
Operating Segments | Southern Power | Electric Utilities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,216 | 1,733 | 1,938
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  |  |  |  | 517 | 494 | 479
Interest income |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 | 4 | 9
Earnings from equity method investments |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 3
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 147 | 151 | 169
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | (13) | 3 | (56)
Segment net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 266 | 238 | 339
Goodwill |  |  |  |  | 2 |  |  |  | 2 |  | 2 | 2 | 2 | 2 | 2 | 2
Assets held for sale |  |  |  |  | 0 |  |  |  | 0 |  | 618 | 0 | 0 | 0 | 0 | 618
Total assets |  |  |  |  | 13,390 |  |  |  | 13,235 |  | 14,300 | 13,390 | 13,390 | 13,390 | 13,235 | 14,300
Operating Segments | Southern Company Gas |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | 4,380 | 3,434 | 3,792
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  |  |  |  | 536 | 500 | 487
Interest income |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 5 | 3
Earnings from equity method investments |  |  |  |  |  |  |  |  |  |  |  |  |  | 50 | 141 | 157
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 238 | 231 | 232
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | 275 | 173 | 130
Segment net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 539 | 590 | 585
Goodwill |  |  |  |  | 5,015 |  |  |  | 5,015 |  | 5,015 | 5,015 | 5,015 | 5,015 | 5,015 | 5,015
Assets held for sale |  |  |  |  | 0 |  |  |  | 0 |  | 171 | 0 | 0 | 0 | 0 | 171
Total assets |  |  |  |  | 23,560 |  |  |  | 22,630 |  | 21,687 | 23,560 | 23,560 | 23,560 | 22,630 | 21,687
Operating Segments | All Other |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | 582 | 596 | 690
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  |  |  |  | 76 | 77 | 79
Interest income |  |  |  |  |  |  |  |  |  |  |  |  |  | 4 | 6 | 16
Earnings from equity method investments |  |  |  |  |  |  |  |  |  |  |  |  |  | 24 | 12 | 0
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 631 | 614 | 517
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | (227) | (297) | 960
Segment net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | (384) | (592) | 908
Goodwill |  |  |  |  | 263 |  |  |  | 263 |  | 263 | 263 | 263 | 263 | 263 | 263
Assets held for sale |  |  |  |  | 3 |  |  |  | 55 |  | 0 | 3 | 3 | 3 | 55 | 0
Total assets |  |  |  |  | 2,975 |  |  |  | 3,168 |  | 3,511 | 2,975 | 2,975 | 2,975 | 3,168 | 3,511
Intersegment Eliminations |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | (149) | (152) | (158)
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 0
Interest income |  |  |  |  |  |  |  |  |  |  |  |  |  | (3) | (4) | (6)
Earnings from equity method investments |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 | 0 | 0
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 0
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 0
Segment net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | (9) | 6 | (22)
Goodwill |  |  |  |  | 0 |  |  |  | 0 |  | 0 | 0 | 0 | 0 | 0 | 0
Assets held for sale |  |  |  |  | 0 |  |  |  | 0 |  | 0 | 0 | 0 | 0 | 0 | 0
Total assets |  |  |  |  | (775) |  |  |  | (904) |  | (1,148) | (775) | (775) | (775) | (904) | (1,148)
Intersegment Eliminations | Electric Utilities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | (530) | (371) | (412)
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 0
Interest income |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 0
Earnings from equity method investments |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 0
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 0
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 0
Segment net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 0
Goodwill |  |  |  |  | 0 |  |  |  | 0 |  | 0 | 0 | 0 | 0 | 0 | 0
Assets held for sale |  |  |  |  | 0 |  |  |  | 0 |  | 0 | 0 | 0 | 0 | 0 | 0
Total assets |  |  |  |  | (667) |  |  |  | (680) |  | (713) | (667) | (667) | (667) | (680) | (713)
Georgia Power |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | 9,260 | 8,309 | 8,408
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,371 | 1,425 | 981
Operating income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 568 | 1,972 | 2,461
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 421 | 425 | 409
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | (168) | 152 | 472
Total assets |  |  |  |  | 48,461 |  |  |  | 47,080 |  |  | 48,461 | 48,461 | 48,461 | 47,080 |
Segment and Related Information (Textual) [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated loss on Plant Vogtle Units 3 and 4 |  |  |  |  | 480 | $ 264 | 460 | $ 48 |  |  |  |  |  | 1,692 | 325 | 0
Estimated loss on Plant Vogtle Units 3 and 4, net of tax |  |  |  |  | 358 | 197 | 343 | $ 36 |  |  |  |  |  |  |  |
Georgia Power | Traditional Electric Operating Companies | Plant Vogtle Units 3 and 4 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment and Related Information (Textual) [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated loss on Plant Vogtle Units 3 and 4 |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,700 | 325 |
Estimated loss on Plant Vogtle Units 3 and 4, net of tax |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,300 | 242 |
Southern Power |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,216 | 1,733 | 1,938
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  |  |  |  | 517 | 494 | 479
Operating income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 291 | 342 | 395
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 147 | 151 | 169
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | (13) | 3 | (56)
Segment net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 266 | 238 | 339
Total assets |  |  |  |  | 13,390 |  |  |  | 13,235 |  |  | 13,390 | 13,390 | 13,390 | 13,235 |
Segment and Related Information (Textual) [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on dispositions |  |  |  |  |  |  |  |  |  |  |  |  |  | 41 | 39 | 24
Southern Power | Wind Generating Facility |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment and Related Information (Textual) [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on dispositions |  |  |  |  |  |  |  |  |  |  |  |  |  | 37 |  | 17
Gain (loss) on dispositions, after tax |  |  |  |  |  |  |  |  |  |  |  |  |  | 28 |  |
Southern Company Gas |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | 4,380 | 3,434 | 3,792
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  |  |  |  | 536 | 500 | 487
Operating income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,055 | 812 | 770
Earnings from equity method investments |  |  |  |  |  |  |  |  |  |  |  |  |  | 50 | 141 | 157
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 238 | 231 | 232
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | 275 | 173 | 130
Segment net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 539 | 590 | 585
Goodwill |  |  |  |  | 5,015 |  |  |  | 5,015 |  |  | 5,015 | 5,015 | 5,015 | 5,015 |
Total assets |  |  |  |  | 23,560 |  |  |  | 22,630 |  | 21,687 | 23,560 | 23,560 | 23,560 | 22,630 | 21,687
Segment and Related Information (Textual) [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on dispositions |  |  |  |  |  |  |  |  |  |  |  |  |  | 127 | 22 | 0
Impairment charges |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 115
Southern Company Gas | PennEast Pipeline |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Earnings from equity method investments |  |  |  |  |  |  |  |  |  |  |  |  |  | (81) | 7 | 6
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | 7 |  |
Segment and Related Information (Textual) [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Impairment charges |  |  |  |  |  | 2 | 82 |  |  |  |  |  |  | 84 |  |
Impairment charges, after tax |  |  |  |  |  | $ 2 | $ 58 |  |  |  |  |  |  | 67 |  |
Southern Company Gas | Gas distribution operations |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Goodwill |  |  |  |  | 4,034 |  |  |  | 4,034 |  |  | 4,034 | 4,034 | 4,034 | 4,034 |
Southern Company Gas | Gas marketing services |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Goodwill |  |  |  |  | 981 |  |  |  | 981 |  |  | 981 | 981 | 981 | 981 |
Southern Company Gas | Operating Segments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | 4,374 | 3,466 | 3,810
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  |  |  |  | 505 | 470 | 454
Operating income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,095 | 814 | 924
Earnings from equity method investments |  |  |  |  |  |  |  |  |  |  |  |  |  | 50 | 141 | 162
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 237 | 228 | 225
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | 213 | 178 | 200
Segment net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 626 | 592 | 677
Total assets |  |  |  |  | 23,971 |  |  |  | 23,040 |  | 22,228 | 23,971 | 23,971 | 23,971 | 23,040 | 22,228
Southern Company Gas | Operating Segments | All Other |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | 38 | 36 | 44
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  |  |  |  | 31 | 30 | 33
Operating income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | (40) | (7) | (154)
Earnings from equity method investments |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | (5)
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 | 3 | 7
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | 62 | (5) | (70)
Segment net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | (87) | (2) | (92)
Total assets |  |  |  |  | 12,114 |  |  |  | 11,336 |  | 10,759 | 12,114 | 12,114 | 12,114 | 11,336 | 10,759
Southern Company Gas | Operating Segments | Gas distribution operations |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | 3,679 | 2,952 | 3,028
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  |  |  |  | 482 | 442 | 422
Operating income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 708 | 655 | 573
Earnings from equity method investments |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 0
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 207 | 192 | 187
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | 120 | 114 | 63
Segment net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 412 | 390 | 337
Total assets |  |  |  |  | 20,917 |  |  |  | 19,090 |  | 18,204 | 20,917 | 20,917 | 20,917 | 19,090 | 18,204
Southern Company Gas | Operating Segments | Gas Pipeline Investments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | 32 | 32 | 32
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 | 5 | 5
Operating income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 21 | 20 | 20
Earnings from equity method investments |  |  |  |  |  |  |  |  |  |  |  |  |  | 50 | 141 | 162
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 25 | 29 | 30
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | 27 | 33 | 58
Segment net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 19 | 99 | 94
Total assets |  |  |  |  | 1,467 |  |  |  | 1,597 |  | 1,678 | 1,467 | 1,467 | 1,467 | 1,597 | 1,678
Southern Company Gas | Operating Segments | Wholesale gas services |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | 188 | 74 | 294
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 1 | 1
Operating income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 241 | 20 | 219
Earnings from equity method investments |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 0
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 | 4 | 5
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | 32 | 3 | 52
Segment net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 107 | 14 | 163
Total assets |  |  |  |  | 31 |  |  |  | 850 |  | 850 | 31 | 31 | 31 | 850 | 850
Southern Company Gas | Operating Segments | Gas marketing services |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | 475 | 408 | 456
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  |  |  |  | 18 | 22 | 26
Operating income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 125 | 119 | 112
Earnings from equity method investments |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 0
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 | 3 | 3
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | 34 | 28 | 27
Segment net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 88 | 89 | 83
Total assets |  |  |  |  | 1,556 |  |  |  | 1,503 |  | 1,496 | 1,556 | 1,556 | 1,556 | 1,503 | 1,496
Southern Company Gas | Intersegment Eliminations |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total operating revenues |  |  |  |  |  |  |  |  |  |  |  |  |  | (32) | (68) | (62)
Depreciation and amortization |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 0
Operating income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 5 | 0
Earnings from equity method investments |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 0
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 0
Income taxes (benefit) |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 0
Segment net income (loss) |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 0
Total assets |  |  |  |  | $ (12,525) |  |  |  | $ (11,746) |  | $ (11,300) | (12,525) | (12,525) | (12,525) | (11,746) | (11,300)
Sequent | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Southern Company Gas |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment and Related Information (Textual) [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on dispositions |  | $ 121 |  |  |  |  |  |  |  |  |  |  |  | 121 |  |
Gain (loss) on dispositions, after tax |  | $ 92 |  |  |  |  |  |  |  |  |  |  |  | 92 |  |
Deferred tax expense, increase from change in appointment rate |  |  |  |  |  |  |  |  |  |  |  | $ 85 | $ 85 | $ 85 |  |
Mankato | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Southern Power |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment and Related Information (Textual) [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on dispositions |  |  | $ 39 |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on dispositions, after tax |  |  | $ 23 |  |  |  |  |  |  |  |  |  |  |  |  |
Gain on sale |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 39 |
Gain on sale, after tax |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 23 |
Plant Nacogdoches | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Southern Power |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment and Related Information (Textual) [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on dispositions |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 23
Gain (loss) on dispositions, after tax |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 88
Gulf Power | Disposal Group, Disposed of by Sale, Not Discontinued Operations |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment and Related Information (Textual) [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on dispositions |  |  |  | $ 2,600 |  |  |  |  |  |  |  |  |  |  |  | 2,600
Gain (loss) on dispositions, after tax |  |  |  | $ 1,400 |  |  |  |  |  |  |  |  |  |  |  | 1,400
PowerSecure International, Inc. Lighting Business | Disposal Group, Disposed of by Sale, Not Discontinued Operations |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment and Related Information (Textual) [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on dispositions |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (58)
Gain (loss) on dispositions, after tax |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (52)
Natural Gas Storage Facility | Southern Company Gas |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment and Related Information (Textual) [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Impairment charges |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 115
Impairment charges, after tax |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 86

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