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Segments Of Business (Tables) | 12 Months Ended
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Dec. 31, 2024
Segment Reporting Information [Line Items] |
Schedule of Segments of Business | Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s reportable segments, which represents the services provided to their customers, and reconciliation to consolidated amounts, was as follows (in millions):
| Utility |  |  |  |
|  |  |  |  | Total |  |  |  | Alliant
|  |  |  |  | Reportable |  |  |  | Energy
2024 | IPL |  | WPL |  | Segments |  | Other |  | Consolidated
Electric utility revenues | $1,747 |  |  | $1,625 |  |  | $3,372 |  |  | N/A |  | $3,372
Gas utility revenues | 250 |  |  | 215 |  |  | 465 |  |  | N/A |  | 465
Other revenues | 49 |  |  | 5 |  |  | 54 |  |  | $90 |  | 144
Total revenues | 2,046 |  |  | 1,845 |  |  | 3,891 |  |  | 90 |  | 3,981
Electric production fuel and purchased power expense | 269 |  |  | 359 |  |  | 628 |  |  | N/A |  | 628
Electric transmission service expense | 417 |  |  | 196 |  |  | 613 |  |  | N/A |  | 613
Cost of gas sold expense | 123 |  |  | 101 |  |  | 224 |  |  | N/A |  | 224
Asset valuation charge for IPL’s Lansing Generation Station | 60 |  |  | — |  |  | 60 |  |  | N/A |  | 60
Other operation and maintenance expense | 358 |  |  | 279 |  |  | 637 |  |  | 39 |  | 676
Other segment items: |  |  |  |  |  |  |  |  |
Depreciation and amortization expense | 404 |  |  | 357 |  |  | 761 |  |  | 11 |  | 772
Interest expense | 177 |  | 165 |  | 342 |  | 107 |  | 449
Equity income from unconsolidated investments, net | — |  |  | (2) |  |  | (2) |  |  | (59) |  | (61)
Income tax expense (benefit) | (129) |  |  | 11 |  | (118) |  |  | 4 |  | (114)
Other (a) | 5 |  |  | 34 |  | 39 |  |  | 5 |  | 44
Net income (loss) | 362 |  | 345 |  | 707 |  | (17) |  | 690
Total assets | 11,407 |  |  | 10,106 |  |  | 21,513 |  |  | 1,201 |  | 22,714
Investments in equity method subsidiaries | 5 |  |  | 17 |  |  | 22 |  |  | 601 |  | 623
Construction and acquisition expenditures | 1,224 |  |  | 828 |  |  | 2,052 |  |  | 197 |  | 2,249
| Utility |  |  |  |
|  |  |  |  | Total |  |  |  | Alliant
|  |  |  |  | Reportable |  |  |  | Energy
2023 (amounts may not foot due to rounding) | IPL |  | WPL |  | Segments |  | Other |  | Consolidated
Electric utility revenues | $1,761 |  |  | $1,584 |  |  | $3,345 |  |  | N/A |  | $3,345
Gas utility revenues | 300 |  |  | 240 |  |  | 540 |  |  | N/A |  | 540
Other revenues | 49 |  |  | 3 |  |  | 52 |  |  | $90 |  | 142
Total revenues | 2,110 |  |  | 1,827 |  |  | 3,937 |  |  | 90 |  | 4,027
Electric production fuel and purchased power expense | 282 |  |  | 455 |  |  | 737 |  |  | N/A |  | 736
Electric transmission service expense | 420 |  |  | 163 |  |  | 583 |  |  | N/A |  | 583
Cost of gas sold expense | 166 |  |  | 134 |  |  | 300 |  |  | N/A |  | 299
Other operation and maintenance expense | 353 |  |  | 271 |  |  | 624 |  |  | 51 |  | 675
Other segment items: |  |  |  |  |  |  |  |  |
Depreciation and amortization expense | 388 |  |  | 280 |  |  | 668 |  |  | 8 |  | 676
Interest expense | 155 |  |  | 149 |  |  | 304 |  |  | 90 |  | 394
Equity income from unconsolidated investments, net | — |  |  | (3) |  |  | (3) |  |  | (58) |  | (61)
Income tax expense (benefit) | (58) |  |  | 60 |  |  | 2 |  |  | 2 |  | 4
Other (a) | 38 |  |  | (27) |  |  | 11 |  |  | 5 |  | 18
Net income (loss) | 366 |  |  | 345 |  |  | 711 |  |  | (8) |  | 703
Total assets | 10,489 |  |  | 9,634 |  |  | 20,123 |  |  | 1,114 |  | 21,237
Investments in equity method subsidiaries | 5 |  |  | 16 |  |  | 21 |  |  | 564 |  | 585
Construction and acquisition expenditures | 712 |  |  | 1,019 |  |  | 1,731 |  |  | 123 |  | 1,854
| Utility |  |  |  |
|  |  |  |  | Total |  |  |  | Alliant
|  |  |  |  | Reportable |  |  |  | Energy
2022 | IPL |  | WPL |  | Segments |  | Other |  | Consolidated
Electric utility revenues | $1,859 |  |  | $1,562 |  |  | $3,421 |  |  | N/A |  | $3,421
Gas utility revenues | 351 |  |  | 291 |  |  | 642 |  |  | N/A |  | 642
Other revenues | 46 |  |  | 3 |  |  | 49 |  |  | $93 |  | 142
Total revenues | 2,256 |  |  | 1,856 |  |  | 4,112 |  |  | 93 |  | 4,205
Electric production fuel and purchased power expense | 383 |  |  | 447 |  |  | 830 |  |  | N/A |  | 830
Electric transmission service expense | 407 |  |  | 166 |  |  | 573 |  |  | N/A |  | 573
Cost of gas sold expense | 206 |  |  | 183 |  |  | 389 |  |  | N/A |  | 389
Other operation and maintenance expense | 369 |  |  | 278 |  |  | 647 |  |  | 57 |  | 704
Other segment items: |  |  |  |  |  |  |  |  |
Depreciation and amortization expense | 381 |  |  | 283 |  |  | 664 |  |  | 7 |  | 671
Interest expense | 148 |  |  | 121 |  |  | 269 |  |  | 56 |  | 325
Equity income from unconsolidated investments, net | — |  |  | (1) |  |  | (1) |  |  | (50) |  | (51)
Income tax expense (benefit) | (50) |  |  | 66 |  |  | 16 |  |  | 6 |  | 22
Other (a) | 52 |  |  | (2) |  |  | 50 |  |  | 6 |  | 56
Net income | 360 |  |  | 315 |  |  | 675 |  |  | 11 |  | 686
Total assets | 10,075 |  |  | 8,987 |  |  | 19,062 |  |  | 1,101 |  | 20,163
Investments in equity method subsidiaries | 5 |  |  | 15 |  |  | 20 |  |  | 522 |  | 542
Construction and acquisition expenditures | 372 |  |  | 1,020 |  |  | 1,392 |  |  | 92 |  | 1,484
(a)Other segment items for each reportable segment include AFUDC, taxes other than income taxes, interest income, and other miscellaneous income and deductions.
IPL [Member] |
Segment Reporting Information [Line Items] |
Schedule of Segments of Business | Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s reportable segments, which represents the services provided to their customers, and reconciliation to consolidated amounts, was as follows (in millions):
| Utility |  |  |  |
|  |  |  |  | Total |  |  |  | Alliant
|  |  |  |  | Reportable |  |  |  | Energy
2024 | IPL |  | WPL |  | Segments |  | Other |  | Consolidated
Electric utility revenues | $1,747 |  |  | $1,625 |  |  | $3,372 |  |  | N/A |  | $3,372
Gas utility revenues | 250 |  |  | 215 |  |  | 465 |  |  | N/A |  | 465
Other revenues | 49 |  |  | 5 |  |  | 54 |  |  | $90 |  | 144
Total revenues | 2,046 |  |  | 1,845 |  |  | 3,891 |  |  | 90 |  | 3,981
Electric production fuel and purchased power expense | 269 |  |  | 359 |  |  | 628 |  |  | N/A |  | 628
Electric transmission service expense | 417 |  |  | 196 |  |  | 613 |  |  | N/A |  | 613
Cost of gas sold expense | 123 |  |  | 101 |  |  | 224 |  |  | N/A |  | 224
Asset valuation charge for IPL’s Lansing Generation Station | 60 |  |  | — |  |  | 60 |  |  | N/A |  | 60
Other operation and maintenance expense | 358 |  |  | 279 |  |  | 637 |  |  | 39 |  | 676
Other segment items: |  |  |  |  |  |  |  |  |
Depreciation and amortization expense | 404 |  |  | 357 |  |  | 761 |  |  | 11 |  | 772
Interest expense | 177 |  | 165 |  | 342 |  | 107 |  | 449
Equity income from unconsolidated investments, net | — |  |  | (2) |  |  | (2) |  |  | (59) |  | (61)
Income tax expense (benefit) | (129) |  |  | 11 |  | (118) |  |  | 4 |  | (114)
Other (a) | 5 |  |  | 34 |  | 39 |  |  | 5 |  | 44
Net income (loss) | 362 |  | 345 |  | 707 |  | (17) |  | 690
Total assets | 11,407 |  |  | 10,106 |  |  | 21,513 |  |  | 1,201 |  | 22,714
Investments in equity method subsidiaries | 5 |  |  | 17 |  |  | 22 |  |  | 601 |  | 623
Construction and acquisition expenditures | 1,224 |  |  | 828 |  |  | 2,052 |  |  | 197 |  | 2,249
| Utility |  |  |  |
|  |  |  |  | Total |  |  |  | Alliant
|  |  |  |  | Reportable |  |  |  | Energy
2023 (amounts may not foot due to rounding) | IPL |  | WPL |  | Segments |  | Other |  | Consolidated
Electric utility revenues | $1,761 |  |  | $1,584 |  |  | $3,345 |  |  | N/A |  | $3,345
Gas utility revenues | 300 |  |  | 240 |  |  | 540 |  |  | N/A |  | 540
Other revenues | 49 |  |  | 3 |  |  | 52 |  |  | $90 |  | 142
Total revenues | 2,110 |  |  | 1,827 |  |  | 3,937 |  |  | 90 |  | 4,027
Electric production fuel and purchased power expense | 282 |  |  | 455 |  |  | 737 |  |  | N/A |  | 736
Electric transmission service expense | 420 |  |  | 163 |  |  | 583 |  |  | N/A |  | 583
Cost of gas sold expense | 166 |  |  | 134 |  |  | 300 |  |  | N/A |  | 299
Other operation and maintenance expense | 353 |  |  | 271 |  |  | 624 |  |  | 51 |  | 675
Other segment items: |  |  |  |  |  |  |  |  |
Depreciation and amortization expense | 388 |  |  | 280 |  |  | 668 |  |  | 8 |  | 676
Interest expense | 155 |  |  | 149 |  |  | 304 |  |  | 90 |  | 394
Equity income from unconsolidated investments, net | — |  |  | (3) |  |  | (3) |  |  | (58) |  | (61)
Income tax expense (benefit) | (58) |  |  | 60 |  |  | 2 |  |  | 2 |  | 4
Other (a) | 38 |  |  | (27) |  |  | 11 |  |  | 5 |  | 18
Net income (loss) | 366 |  |  | 345 |  |  | 711 |  |  | (8) |  | 703
Total assets | 10,489 |  |  | 9,634 |  |  | 20,123 |  |  | 1,114 |  | 21,237
Investments in equity method subsidiaries | 5 |  |  | 16 |  |  | 21 |  |  | 564 |  | 585
Construction and acquisition expenditures | 712 |  |  | 1,019 |  |  | 1,731 |  |  | 123 |  | 1,854
| Utility |  |  |  |
|  |  |  |  | Total |  |  |  | Alliant
|  |  |  |  | Reportable |  |  |  | Energy
2022 | IPL |  | WPL |  | Segments |  | Other |  | Consolidated
Electric utility revenues | $1,859 |  |  | $1,562 |  |  | $3,421 |  |  | N/A |  | $3,421
Gas utility revenues | 351 |  |  | 291 |  |  | 642 |  |  | N/A |  | 642
Other revenues | 46 |  |  | 3 |  |  | 49 |  |  | $93 |  | 142
Total revenues | 2,256 |  |  | 1,856 |  |  | 4,112 |  |  | 93 |  | 4,205
Electric production fuel and purchased power expense | 383 |  |  | 447 |  |  | 830 |  |  | N/A |  | 830
Electric transmission service expense | 407 |  |  | 166 |  |  | 573 |  |  | N/A |  | 573
Cost of gas sold expense | 206 |  |  | 183 |  |  | 389 |  |  | N/A |  | 389
Other operation and maintenance expense | 369 |  |  | 278 |  |  | 647 |  |  | 57 |  | 704
Other segment items: |  |  |  |  |  |  |  |  |
Depreciation and amortization expense | 381 |  |  | 283 |  |  | 664 |  |  | 7 |  | 671
Interest expense | 148 |  |  | 121 |  |  | 269 |  |  | 56 |  | 325
Equity income from unconsolidated investments, net | — |  |  | (1) |  |  | (1) |  |  | (50) |  | (51)
Income tax expense (benefit) | (50) |  |  | 66 |  |  | 16 |  |  | 6 |  | 22
Other (a) | 52 |  |  | (2) |  |  | 50 |  |  | 6 |  | 56
Net income | 360 |  |  | 315 |  |  | 675 |  |  | 11 |  | 686
Total assets | 10,075 |  |  | 8,987 |  |  | 19,062 |  |  | 1,101 |  | 20,163
Investments in equity method subsidiaries | 5 |  |  | 15 |  |  | 20 |  |  | 522 |  | 542
Construction and acquisition expenditures | 372 |  |  | 1,020 |  |  | 1,392 |  |  | 92 |  | 1,484
(a)Other segment items for each reportable segment include AFUDC, taxes other than income taxes, interest income, and other miscellaneous income and deductions.
WPL [Member] |
Segment Reporting Information [Line Items] |
Schedule of Segments of Business | Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s reportable segments, which represents the services provided to their customers, and reconciliation to consolidated amounts, was as follows (in millions):
| Utility |  |  |  |
|  |  |  |  | Total |  |  |  | Alliant
|  |  |  |  | Reportable |  |  |  | Energy
2024 | IPL |  | WPL |  | Segments |  | Other |  | Consolidated
Electric utility revenues | $1,747 |  |  | $1,625 |  |  | $3,372 |  |  | N/A |  | $3,372
Gas utility revenues | 250 |  |  | 215 |  |  | 465 |  |  | N/A |  | 465
Other revenues | 49 |  |  | 5 |  |  | 54 |  |  | $90 |  | 144
Total revenues | 2,046 |  |  | 1,845 |  |  | 3,891 |  |  | 90 |  | 3,981
Electric production fuel and purchased power expense | 269 |  |  | 359 |  |  | 628 |  |  | N/A |  | 628
Electric transmission service expense | 417 |  |  | 196 |  |  | 613 |  |  | N/A |  | 613
Cost of gas sold expense | 123 |  |  | 101 |  |  | 224 |  |  | N/A |  | 224
Asset valuation charge for IPL’s Lansing Generation Station | 60 |  |  | — |  |  | 60 |  |  | N/A |  | 60
Other operation and maintenance expense | 358 |  |  | 279 |  |  | 637 |  |  | 39 |  | 676
Other segment items: |  |  |  |  |  |  |  |  |
Depreciation and amortization expense | 404 |  |  | 357 |  |  | 761 |  |  | 11 |  | 772
Interest expense | 177 |  | 165 |  | 342 |  | 107 |  | 449
Equity income from unconsolidated investments, net | — |  |  | (2) |  |  | (2) |  |  | (59) |  | (61)
Income tax expense (benefit) | (129) |  |  | 11 |  | (118) |  |  | 4 |  | (114)
Other (a) | 5 |  |  | 34 |  | 39 |  |  | 5 |  | 44
Net income (loss) | 362 |  | 345 |  | 707 |  | (17) |  | 690
Total assets | 11,407 |  |  | 10,106 |  |  | 21,513 |  |  | 1,201 |  | 22,714
Investments in equity method subsidiaries | 5 |  |  | 17 |  |  | 22 |  |  | 601 |  | 623
Construction and acquisition expenditures | 1,224 |  |  | 828 |  |  | 2,052 |  |  | 197 |  | 2,249
| Utility |  |  |  |
|  |  |  |  | Total |  |  |  | Alliant
|  |  |  |  | Reportable |  |  |  | Energy
2023 (amounts may not foot due to rounding) | IPL |  | WPL |  | Segments |  | Other |  | Consolidated
Electric utility revenues | $1,761 |  |  | $1,584 |  |  | $3,345 |  |  | N/A |  | $3,345
Gas utility revenues | 300 |  |  | 240 |  |  | 540 |  |  | N/A |  | 540
Other revenues | 49 |  |  | 3 |  |  | 52 |  |  | $90 |  | 142
Total revenues | 2,110 |  |  | 1,827 |  |  | 3,937 |  |  | 90 |  | 4,027
Electric production fuel and purchased power expense | 282 |  |  | 455 |  |  | 737 |  |  | N/A |  | 736
Electric transmission service expense | 420 |  |  | 163 |  |  | 583 |  |  | N/A |  | 583
Cost of gas sold expense | 166 |  |  | 134 |  |  | 300 |  |  | N/A |  | 299
Other operation and maintenance expense | 353 |  |  | 271 |  |  | 624 |  |  | 51 |  | 675
Other segment items: |  |  |  |  |  |  |  |  |
Depreciation and amortization expense | 388 |  |  | 280 |  |  | 668 |  |  | 8 |  | 676
Interest expense | 155 |  |  | 149 |  |  | 304 |  |  | 90 |  | 394
Equity income from unconsolidated investments, net | — |  |  | (3) |  |  | (3) |  |  | (58) |  | (61)
Income tax expense (benefit) | (58) |  |  | 60 |  |  | 2 |  |  | 2 |  | 4
Other (a) | 38 |  |  | (27) |  |  | 11 |  |  | 5 |  | 18
Net income (loss) | 366 |  |  | 345 |  |  | 711 |  |  | (8) |  | 703
Total assets | 10,489 |  |  | 9,634 |  |  | 20,123 |  |  | 1,114 |  | 21,237
Investments in equity method subsidiaries | 5 |  |  | 16 |  |  | 21 |  |  | 564 |  | 585
Construction and acquisition expenditures | 712 |  |  | 1,019 |  |  | 1,731 |  |  | 123 |  | 1,854
| Utility |  |  |  |
|  |  |  |  | Total |  |  |  | Alliant
|  |  |  |  | Reportable |  |  |  | Energy
2022 | IPL |  | WPL |  | Segments |  | Other |  | Consolidated
Electric utility revenues | $1,859 |  |  | $1,562 |  |  | $3,421 |  |  | N/A |  | $3,421
Gas utility revenues | 351 |  |  | 291 |  |  | 642 |  |  | N/A |  | 642
Other revenues | 46 |  |  | 3 |  |  | 49 |  |  | $93 |  | 142
Total revenues | 2,256 |  |  | 1,856 |  |  | 4,112 |  |  | 93 |  | 4,205
Electric production fuel and purchased power expense | 383 |  |  | 447 |  |  | 830 |  |  | N/A |  | 830
Electric transmission service expense | 407 |  |  | 166 |  |  | 573 |  |  | N/A |  | 573
Cost of gas sold expense | 206 |  |  | 183 |  |  | 389 |  |  | N/A |  | 389
Other operation and maintenance expense | 369 |  |  | 278 |  |  | 647 |  |  | 57 |  | 704
Other segment items: |  |  |  |  |  |  |  |  |
Depreciation and amortization expense | 381 |  |  | 283 |  |  | 664 |  |  | 7 |  | 671
Interest expense | 148 |  |  | 121 |  |  | 269 |  |  | 56 |  | 325
Equity income from unconsolidated investments, net | — |  |  | (1) |  |  | (1) |  |  | (50) |  | (51)
Income tax expense (benefit) | (50) |  |  | 66 |  |  | 16 |  |  | 6 |  | 22
Other (a) | 52 |  |  | (2) |  |  | 50 |  |  | 6 |  | 56
Net income | 360 |  |  | 315 |  |  | 675 |  |  | 11 |  | 686
Total assets | 10,075 |  |  | 8,987 |  |  | 19,062 |  |  | 1,101 |  | 20,163
Investments in equity method subsidiaries | 5 |  |  | 15 |  |  | 20 |  |  | 522 |  | 542
Construction and acquisition expenditures | 372 |  |  | 1,020 |  |  | 1,392 |  |  | 92 |  | 1,484
(a)Other segment items for each reportable segment include AFUDC, taxes other than income taxes, interest income, and other miscellaneous income and deductions.

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- Definition Tabular disclosure of the profit or loss and total assets for each reportable segment. An entity discloses certain information on each reportable segment if the amounts (a) are included in the measure of segment profit or loss reviewed by the chief operating decision maker or (b) are otherwise regularly provided to the chief operating decision maker, even if not included in that measure of segment profit or loss. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 25 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482810/280-10-50-25 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482810/280-10-50-22 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 30 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482810/280-10-50-30 + Details
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