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Segments Of Business (Tables) | 12 Months Ended
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Dec. 31, 2023
Segment Reporting Information [Line Items] |
Schedule of Segments of Business | Certain financial information relating to Alliant Energy’s business segments, which represent the services provided to its customers, was as follows (in millions):
|  |  |  |  |  |  |  |  | ATC Holdings, |  |
| Utility |  | Non-utility, |  | Alliant Energy
2023 | Electric |  | Gas |  | Other |  | Total |  | Parent and Other |  | Consolidated
Revenues | $3,345 |  |  | $540 |  |  | $52 |  |  | $3,937 |  |  | $90 |  | $4,027
Depreciation and amortization | 602 |  |  | 60 |  |  | 6 |  |  | 668 |  |  | 8 |  | 676
Operating income | 827 |  |  | 70 |  |  | 19 |  |  | 916 |  |  | 27 |  | 943
Interest expense |  |  |  |  |  |  | 304 |  |  | 90 |  | 394
Equity income from unconsolidated investments, net | (3) |  |  | — |  |  | — |  |  | (3) |  |  | (58) |  | (61)
Income taxes |  |  |  |  |  |  | 2 |  |  | 2 |  | 4
Net income (loss) attributable to Alliant Energy common shareowners |  |  |  |  |  |  | 711 |  |  | (8) |  | 703
Total assets | 17,833 |  |  | 1,684 |  |  | 606 |  |  | 20,123 |  |  | 1,114 |  | 21,237
Investments in equity method subsidiaries | 21 |  |  | — |  |  | — |  |  | 21 |  |  | 564 |  | 585
Construction and acquisition expenditures | 1,641 |  |  | 90 |  |  | — |  |  | 1,731 |  |  | 123 |  | 1,854
|  |  |  |  |  |  |  |  | ATC Holdings, |  |
| Utility |  | Non-utility, |  | Alliant Energy
2022 | Electric |  | Gas |  | Other |  | Total |  | Parent and Other |  | Consolidated
Revenues | $3,421 |  |  | $642 |  |  | $49 |  |  | $4,112 |  |  | $93 |  | $4,205
Depreciation and amortization | 601 |  |  | 56 |  |  | 7 |  |  | 664 |  |  | 7 |  | 671
Operating income | 805 |  |  | 97 |  |  | 3 |  |  | 905 |  |  | 23 |  | 928
Interest expense |  |  |  |  |  |  | 269 |  |  | 56 |  | 325
Equity income from unconsolidated investments, net | (1) |  |  | — |  |  | — |  |  | (1) |  |  | (50) |  | (51)
Income taxes |  |  |  |  |  |  | 16 |  |  | 6 |  | 22
Net income attributable to Alliant Energy common shareowners |  |  |  |  |  |  | 675 |  |  | 11 |  | 686
Total assets | 16,571 |  |  | 1,631 |  |  | 860 |  |  | 19,062 |  |  | 1,101 |  | 20,163
Investments in equity method subsidiaries | 20 |  |  | — |  |  | — |  |  | 20 |  |  | 522 |  | 542
Construction and acquisition expenditures | 1,318 |  |  | 74 |  |  | — |  |  | 1,392 |  |  | 92 |  | 1,484
|  |  |  |  |  |  |  |  | ATC Holdings, |  |
| Utility |  | Non-utility, |  | Alliant Energy
2021 | Electric |  | Gas |  | Other |  | Total |  | Parent and Other |  | Consolidated
Revenues | $3,081 |  |  | $456 |  |  | $49 |  |  | $3,586 |  |  | $83 |  | $3,669
Depreciation and amortization | 591 |  |  | 54 |  |  | 6 |  |  | 651 |  |  | 6 |  | 657
Operating income (loss) | 716 |  |  | 63 |  |  | (11) |  |  | 768 |  |  | 27 |  | 795
Interest expense |  |  |  |  |  |  | 244 |  |  | 33 |  | 277
Equity income from unconsolidated investments, net | (2) |  |  | — |  |  | — |  |  | (2) |  |  | (60) |  | (62)
Income tax expense (benefit) |  |  |  |  |  |  | (87) |  |  | 13 |  | (74)
Net income attributable to Alliant Energy common shareowners |  |  |  |  |  |  | 618 |  |  | 41 |  | 659
Total assets | 14,924 |  |  | 1,487 |  |  | 1,103 |  |  | 17,514 |  |  | 1,039 |  | 18,553
Investments in equity method subsidiaries | 17 |  |  | — |  |  | — |  |  | 17 |  |  | 491 |  | 508
Construction and acquisition expenditures | 980 |  |  | 90 |  |  | — |  |  | 1,070 |  |  | 99 |  | 1,169
IPL [Member] |
Segment Reporting Information [Line Items] |
Schedule of Segments of Business | Certain financial information relating to IPL’s business segments, which represent the services provided to its customers, was as follows (in millions):
2023 | Electric |  | Gas |  | Other |  | Total
Revenues | $1,761 |  | $300 |  | $49 |  | $2,110 |
Depreciation and amortization | 348 |  | 34 |  | 6 |  | 388 |
Operating income | 390 |  | 35 |  | 19 |  | 444 |
Interest expense |  |  |  |  |  |  | 155 |
Income tax benefit |  |  |  |  |  |  | (58) |
Net income available for common stock |  |  |  |  |  |  | 366 |
Total assets | 9,311 |  |  | 921 |  |  | 257 |  |  | 10,489 |
Construction and acquisition expenditures | 671 |  |  | 41 |  |  | — |  |  | 712 |
2022 | Electric |  | Gas |  | Other |  | Total
Revenues | $1,859 |  |  | $351 |  |  | $46 |  |  | $2,256 |
Depreciation and amortization | 342 |  |  | 32 |  |  | 7 |  |  | 381 |
Operating income | 397 |  |  | 53 |  |  | 3 |  |  | 453 |
Interest expense |  |  |  |  |  |  | 148 |
Income tax benefit |  |  |  |  |  |  | (50) |
Net income available for common stock |  |  |  |  |  |  | 360 |
Total assets | 8,686 |  |  | 872 |  |  | 517 |  |  | 10,075 |
Construction and acquisition expenditures | 336 |  |  | 36 |  |  | — |  |  | 372 |
2021 | Electric |  | Gas |  | Other |  | Total
Revenues | $1,752 |  |  | $265 |  |  | $46 |  |  | $2,063 |
Depreciation and amortization | 338 |  |  | 31 |  |  | 6 |  |  | 375 |
Operating income (loss) | 420 |  |  | 43 |  |  | (3) |  |  | 460 |
Interest expense |  |  |  |  |  |  | 139 |
Income tax benefit |  |  |  |  |  |  | (36) |
Net income available for common stock |  |  |  |  |  |  | 350 |
Total assets | 8,602 |  |  | 819 |  |  | 575 |  |  | 9,996 |
Construction and acquisition expenditures | 342 |  |  | 42 |  |  | — |  |  | 384 |
WPL [Member] |
Segment Reporting Information [Line Items] |
Schedule of Segments of Business | Certain financial information relating to WPL’s business segments, which represent the services provided to its customers, was as follows (in millions):
2023 | Electric |  | Gas |  | Other |  | Total
Revenues | $1,584 |  |  | $240 |  |  | $3 |  |  | $1,827 |
Depreciation and amortization | 254 |  |  | 26 |  |  | — |  |  | 280 |
Operating income | 437 |  |  | 35 |  |  | — |  |  | 472 |
Interest expense |  |  |  |  |  |  | 149 |
Income taxes |  |  |  |  |  |  | 60 |
Net income |  |  |  |  |  |  | 345 |
Total assets | 8,522 |  |  | 763 |  |  | 349 |  |  | 9,634 |
Construction and acquisition expenditures | 970 |  |  | 49 |  |  | — |  |  | 1,019 |
2022 | Electric |  | Gas |  | Other |  | Total
Revenues | $1,562 |  |  | $291 |  |  | $3 |  |  | $1,856 |
Depreciation and amortization | 259 |  |  | 24 |  |  | — |  |  | 283 |
Operating income | 408 |  |  | 44 |  |  | — |  |  | 452 |
Interest expense |  |  |  |  |  |  | 121 |
Income taxes |  |  |  |  |  |  | 66 |
Net income |  |  |  |  |  |  | 315 |
Total assets | 7,885 |  |  | 759 |  |  | 343 |  |  | 8,987 |
Construction and acquisition expenditures | 982 |  |  | 38 |  |  | — |  |  | 1,020 |
2021 | Electric |  | Gas |  | Other |  | Total
Revenues | $1,329 |  |  | $191 |  |  | $3 |  |  | $1,523 |
Depreciation and amortization | 253 |  |  | 23 |  |  | — |  |  | 276 |
Operating income (loss) | 296 |  |  | 20 |  |  | (8) |  |  | 308 |
Interest expense |  |  |  |  |  |  | 105 |
Income tax benefit |  |  |  |  |  |  | (51) |
Net income |  |  |  |  |  |  | 268 |
Total assets | 6,322 |  |  | 668 |  |  | 528 |  |  | 7,518 |
Construction and acquisition expenditures | 638 |  |  | 48 |  |  | — |  |  | 686 |

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