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Segments Of Business (Tables) | 12 Months Ended
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Dec. 31, 2021
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
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
|  |  |  |  |  |  |  |  | ATC Holdings, |  |
| Utility |  | Non-utility, |  | Alliant Energy
2020 | Electric |  | Gas |  | Other |  | Total |  | Parent and Other |  | Consolidated
Revenues | $2,920 |  |  | $373 |  |  | $49 |  |  | $3,342 |  |  | $74 |  | $3,416
Depreciation and amortization | 556 |  |  | 49 |  |  | 5 |  |  | 610 |  |  | 5 |  | 615
Operating income (loss) | 643 |  |  | 74 |  |  | (1) |  |  | 716 |  |  | 24 |  | 740
Interest expense |  |  |  |  |  |  | 243 |  |  | 32 |  | 275
Equity income from unconsolidated investments, net | (2) |  |  | — |  |  | — |  |  | (2) |  |  | (59) |  | (61)
Income tax expense (benefit) |  |  |  |  |  |  | (66) |  |  | 9 |  | (57)
Net income attributable to Alliant Energy common shareowners |  |  |  |  |  |  | 573 |  |  | 41 |  | 614
Total assets | 14,358 |  |  | 1,413 |  |  | 990 |  |  | 16,761 |  |  | 949 |  | 17,710
Investments in equity method subsidiaries | 11 |  |  | — |  |  | — |  |  | 11 |  |  | 465 |  | 476
Construction and acquisition expenditures | 1,109 |  |  | 182 |  |  | 2 |  |  | 1,293 |  |  | 73 |  | 1,366
|  |  |  |  |  |  |  |  | ATC Holdings, |  |
| Utility |  | Non-utility, |  | Alliant Energy
2019 | Electric |  | Gas |  | Other |  | Total |  | Parent and Other |  | Consolidated
Revenues | $3,064 |  |  | $455 |  |  | $46 |  |  | $3,565 |  |  | $83 |  | $3,648
Depreciation and amortization | 513 |  |  | 47 |  |  | 3 |  |  | 563 |  |  | 4 |  | 567
Operating income | 679 |  |  | 70 |  |  | 1 |  |  | 750 |  |  | 28 |  | 778
Interest expense |  |  |  |  |  |  | 229 |  |  | 44 |  | 273
Equity income from unconsolidated investments, net | (1) |  |  | — |  |  | — |  |  | (1) |  |  | (52) |  | (53)
Income tax expense (benefit) |  |  |  |  |  |  | 73 |  |  | (4) |  | 69
Net income attributable to Alliant Energy common shareowners |  |  |  |  |  |  | 517 |  |  | 40 |  | 557
Total assets | 13,659 |  |  | 1,269 |  |  | 856 |  |  | 15,784 |  |  | 917 |  | 16,701
Investments in equity method subsidiaries | 9 |  |  | — |  |  | — |  |  | 9 |  |  | 449 |  | 458
Construction and acquisition expenditures | 1,439 |  |  | 100 |  |  | — |  |  | 1,539 |  |  | 101 |  | 1,640
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):
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 |
2020 | Electric |  | Gas |  | Other |  | Total
Revenues | $1,695 |  | $208 |  | $44 |  | $1,947 |
Depreciation and amortization | 321 |  | 30 |  | 5 |  | 356 |
Operating income | 358 |  | 50 |  | 2 |  | 410 |
Interest expense |  |  |  |  |  |  | 139 |
Income tax benefit |  |  |  |  |  |  | (47) |
Net income available for common stock |  |  |  |  |  |  | 324 |
Total assets | 8,518 |  | 766 |  | 565 |  | 9,849 |
Construction and acquisition expenditures | 626 |  | 59 |  | 2 |  | 687 |
2019 | Electric |  | Gas |  | Other |  | Total
Revenues | $1,781 |  | $264 |  | $44 |  | $2,089 |
Depreciation and amortization | 295 |  | 29 |  | 3 |  | 327 |
Operating income | 360 |  | 39 |  | 4 |  | 403 |
Interest expense |  |  |  |  |  |  | 127 |
Income taxes |  |  |  |  |  |  | 24 |
Net income available for common stock |  |  |  |  |  |  | 284 |
Total assets | 8,075 |  | 734 |  | 468 |  | 9,277 |
Construction and acquisition expenditures | 964 |  | 56 |  | — |  | 1,020 |
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):
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 |
2020 | Electric |  | Gas |  | Other |  | Total
Revenues | $1,225 |  |  | $165 |  |  | $5 |  |  | $1,395 |
Depreciation and amortization | 235 |  |  | 19 |  |  | — |  |  | 254 |
Operating income (loss) | 285 |  |  | 24 |  |  | (3) |  |  | 306 |
Interest expense |  |  |  |  |  |  | 104 |
Income tax benefit |  |  |  |  |  |  | (19) |
Net income |  |  |  |  |  |  | 249 |
Total assets | 5,840 |  |  | 647 |  |  | 425 |  |  | 6,912 |
Construction and acquisition expenditures | 483 |  |  | 123 |  |  | — |  |  | 606 |
2019 | Electric |  | Gas |  | Other |  | Total
Revenues | $1,283 |  |  | $191 |  |  | $2 |  |  | $1,476 |
Depreciation and amortization | 218 |  |  | 18 |  |  | — |  |  | 236 |
Operating income (loss) | 319 |  |  | 31 |  |  | (3) |  |  | 347 |
Interest expense |  |  |  |  |  |  | 102 |
Income taxes |  |  |  |  |  |  | 49 |
Net income |  |  |  |  |  |  | 233 |
Total assets | 5,584 |  |  | 535 |  |  | 388 |  |  | 6,507 |
Construction and acquisition expenditures | 475 |  |  | 44 |  |  | — |  |  | 519 |

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