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Segments Of Business (Tables) | 12 Months Ended
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Dec. 31, 2018
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
2018 | Electric |  | Gas |  | Other |  | Total |  | Parent and Other |  | Consolidated
Revenues |  | $3,000.3 |  |  |  | $446.6 |  |  |  | $48.0 |  |  |  | $3,494.9 |  |  |  | $39.6 |  |  |  | $3,534.5 |
Depreciation and amortization | 457.3 |  |  | 42.0 |  |  | 3.6 |  |  | 502.9 |  |  | 4.0 |  |  | 506.9 |
Operating income | 610.2 |  |  | 53.2 |  |  | 0.3 |  |  | 663.7 |  |  | 30.7 |  |  | 694.4 |
Interest expense |  |  |  |  |  |  | 217.2 |  |  | 29.8 |  |  | 247.0 |
Equity income from unconsolidated investments, net | (0.9 | ) |  | — |  |  | — |  |  | (0.9 | ) |  | (53.7 | ) |  | (54.6 | )
Income taxes |  |  |  |  |  |  | 33.0 |  |  | 14.7 |  |  | 47.7 |
Net income attributable to Alliant Energy common shareowners |  |  |  |  |  |  | 472.1 |  |  | 40.0 |  |  | 512.1 |
Total assets | 12,486.3 |  |  | 1,184.4 |  |  | 893.2 |  |  | 14,563.9 |  |  | 862.1 |  |  | 15,426.0 |
Investments in equity method subsidiaries | 8.1 |  |  | — |  |  | — |  |  | 8.1 |  |  | 413.2 |  |  | 421.3 |
Construction and acquisition expenditures | 1,421.1 |  |  | 146.8 |  |  | 0.4 |  |  | 1,568.3 |  |  | 65.6 |  |  | 1,633.9 |
|  |  |  |  |  |  |  |  | ATC Holdings, |  |
| Utility |  | Non-utility, |  | Alliant Energy
2017 | Electric |  | Gas |  | Other |  | Total |  | Parent and Other |  | Consolidated
Revenues |  | $2,894.7 |  |  |  | $400.9 |  |  |  | $47.5 |  |  |  | $3,343.1 |  |  |  | $39.1 |  |  |  | $3,382.2 |
Depreciation and amortization | 412.0 |  |  | 38.2 |  |  | 7.7 |  |  | 457.9 |  |  | 3.9 |  |  | 461.8 |
Operating income (loss) | 601.7 |  |  | 47.7 |  |  | (11.6 | ) |  | 637.8 |  |  | 33.4 |  |  | 671.2 |
Interest expense |  |  |  |  |  |  | 206.2 |  |  | 9.4 |  |  | 215.6 |
Equity income from unconsolidated investments, net | (0.7 | ) |  | — |  |  | — |  |  | (0.7 | ) |  | (44.1 | ) |  | (44.8 | )
Income taxes |  |  |  |  |  |  | 51.0 |  |  | 15.7 |  |  | 66.7 |
Net income attributable to Alliant Energy common shareowners |  |  |  |  |  |  | 403.4 |  |  | 53.9 |  |  | 457.3 |
Total assets | 11,396.2 |  |  | 1,199.8 |  |  | 766.5 |  |  | 13,362.5 |  |  | 825.3 |  |  | 14,187.8 |
Investments in equity method subsidiaries | 8.3 |  |  | — |  |  | — |  |  | 8.3 |  |  | 373.1 |  |  | 381.4 |
Construction and acquisition expenditures | 1,154.9 |  |  | 125.2 |  |  | 1.7 |  |  | 1,281.8 |  |  | 185.1 |  |  | 1,466.9 |
|  |  |  |  |  |  |  |  | ATC Holdings, |  |
| Utility |  | Non-utility, |  | Alliant Energy
2016 | Electric |  | Gas |  | Other |  | Total |  | Parent and Other |  | Consolidated
Revenues |  | $2,875.5 |  |  |  | $355.4 |  |  |  | $48.6 |  |  |  | $3,279.5 |  |  |  | $40.5 |  |  |  | $3,320.0 |
Depreciation and amortization | 367.0 |  |  | 34.2 |  |  | 2.1 |  |  | 403.3 |  |  | 8.3 |  |  | 411.6 |
Operating income (loss) | 586.5 |  |  | 33.0 |  |  | (4.7 | ) |  | 614.8 |  |  | (60.7 | ) |  | 554.1 |
Interest expense |  |  |  |  |  |  | 194.6 |  |  | 1.6 |  |  | 196.2 |
Equity income from unconsolidated investments, net | (0.7 | ) |  | — |  |  | — |  |  | (0.7 | ) |  | (38.9 | ) |  | (39.6 | )
Income tax expense (benefit) |  |  |  |  |  |  | 71.4 |  |  | (12.0 | ) |  | 59.4 |
Net income (loss) attributable to Alliant Energy common shareowners |  |  |  |  |  |  | 385.2 |  |  | (13.7 | ) |  | 371.5 |
Total assets | 10,722.9 |  |  | 1,091.1 |  |  | 781.0 |  |  | 12,595.0 |  |  | 778.8 |  |  | 13,373.8 |
Investments in equity method subsidiaries | 7.7 |  |  | — |  |  | — |  |  | 7.7 |  |  | 318.3 |  |  | 326.0 |
Construction and acquisition expenditures | 994.0 |  |  | 137.1 |  |  | 0.1 |  |  | 1,131.2 |  |  | 65.6 |  |  | 1,196.8 |
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):
2018 | Electric |  | Gas |  | Other |  | Total
Revenues |  | $1,731.1 |  |  |  | $266.2 |  |  |  | $45.0 |  |  |  | $2,042.3 |
Depreciation and amortization | 254.7 |  |  | 25.2 |  |  | 3.6 |  |  | 283.5 |
Operating income | 318.2 |  |  | 28.3 |  |  | 4.3 |  |  | 350.8 |
Interest expense |  |  |  |  |  |  | 119.4 |
Income tax benefit |  |  |  |  |  |  | (3.2 | )
Earnings available for common stock |  |  |  |  |  |  | 264.0 |
Total assets | 7,219.9 |  |  | 687.5 |  |  | 504.0 |  |  | 8,411.4 |
Construction and acquisition expenditures | 890.6 |  |  | 99.7 |  |  | 0.4 |  |  | 990.7 |
2017 | Electric |  | Gas |  | Other |  | Total
Revenues |  | $1,598.9 |  |  |  | $226.0 |  |  |  | $45.4 |  |  |  | $1,870.3 |
Depreciation and amortization | 215.1 |  |  | 22.2 |  |  | 7.7 |  |  | 245.0 |
Operating income (loss) | 287.3 |  |  | 21.7 |  |  | (4.9 | ) |  | 304.1 |
Interest expense |  |  |  |  |  |  | 112.4 |
Income tax benefit |  |  |  |  |  |  | (10.9 | )
Earnings available for common stock |  |  |  |  |  |  | 216.8 |
Total assets | 6,524.4 |  |  | 727.9 |  |  | 353.7 |  |  | 7,606.0 |
Construction and acquisition expenditures | 594.1 |  |  | 80.7 |  |  | 1.2 |  |  | 676.0 |
2016 | Electric |  | Gas |  | Other |  | Total
Revenues |  | $1,569.7 |  |  |  | $204.0 |  |  |  | $46.7 |  |  |  | $1,820.4 |
Depreciation and amortization | 189.4 |  |  | 19.3 |  |  | 2.1 |  |  | 210.8 |
Operating income | 257.8 |  |  | 16.4 |  |  | 3.4 |  |  | 277.6 |
Interest expense |  |  |  |  |  |  | 103.2 |
Income tax benefit |  |  |  |  |  |  | (5.9 | )
Earnings available for common stock |  |  |  |  |  |  | 215.6 |
Total assets | 6,278.2 |  |  | 653.3 |  |  | 373.2 |  |  | 7,304.7 |
Construction and acquisition expenditures | 598.1 |  |  | 91.5 |  |  | 0.1 |  |  | 689.7 |
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):
2018 | Electric |  | Gas |  | Other |  | Total
Revenues |  | $1,269.2 |  |  |  | $180.4 |  |  |  | $3.0 |  |  |  | $1,452.6 |
Depreciation and amortization | 202.6 |  |  | 16.8 |  |  | — |  |  | 219.4 |
Operating income (loss) | 292.0 |  |  | 24.9 |  |  | (4.0 | ) |  | 312.9 |
Interest expense |  |  |  |  |  |  | 97.8 |
Income taxes |  |  |  |  |  |  | 36.2 |
Earnings available for common stock |  |  |  |  |  |  | 208.1 |
Total assets | 5,266.4 |  |  | 496.9 |  |  | 389.2 |  |  | 6,152.5 |
Construction and acquisition expenditures | 530.5 |  |  | 47.1 |  |  | — |  |  | 577.6 |
2017 | Electric |  | Gas |  | Other |  | Total
Revenues |  | $1,295.8 |  |  |  | $174.9 |  |  |  | $2.1 |  |  |  | $1,472.8 |
Depreciation and amortization | 196.9 |  |  | 16.0 |  |  | — |  |  | 212.9 |
Operating income (loss) | 314.4 |  |  | 26.0 |  |  | (6.7 | ) |  | 333.7 |
Interest expense |  |  |  |  |  |  | 93.8 |
Income taxes |  |  |  |  |  |  | 61.9 |
Earnings available for common stock |  |  |  |  |  |  | 186.6 |
Total assets | 4,871.8 |  |  | 471.9 |  |  | 412.8 |  |  | 5,756.5 |
Construction and acquisition expenditures | 592.4 |  |  | 44.5 |  |  | 0.5 |  |  | 637.4 |
2016 | Electric |  | Gas |  | Other |  | Total
Revenues |  | $1,305.8 |  |  |  | $151.4 |  |  |  | $1.9 |  |  |  | $1,459.1 |
Depreciation and amortization | 177.6 |  |  | 14.9 |  |  | — |  |  | 192.5 |
Operating income (loss) | 328.7 |  |  | 16.6 |  |  | (8.1 | ) |  | 337.2 |
Interest expense |  |  |  |  |  |  | 91.4 |
Equity income from unconsolidated investments | (0.7 | ) |  | — |  |  | (39.1 | ) |  | (39.8 | )
Income taxes |  |  |  |  |  |  | 93.3 |
Earnings available for common stock |  |  |  |  |  |  | 190.4 |
Total assets | 4,444.7 |  |  | 437.8 |  |  | 407.8 |  |  | 5,290.3 |
Construction and acquisition expenditures | 395.9 |  |  | 45.6 |  |  | 11.5 |  |  | 453.0 |

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