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Selected Consolidated Quarterly Financial Data (Unaudited) (Tables) | 12 Months Ended
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Dec. 31, 2019
Components Of Selected Consolidated Quarterly Financial Data | All “per share” references refer to earnings per diluted share. Summation of the individual quarters may not equal annual totals due to rounding.
| 2019 |  | 2018
| March 31 |  | June 30 |  | Sep. 30 |  | Dec. 31 |  | March 31 |  | June 30 |  | Sep. 30 |  | Dec. 31
| (in millions, except per share data)
Revenues |  | $987.2 |  |  |  | $790.2 |  |  |  | $990.2 |  |  |  | $880.1 |  |  |  | $916.3 |  |  |  | $816.1 |  |  |  | $928.6 |  |  |  | $873.5 |
Operating income | 176.8 |  |  | 149.8 |  |  | 290.2 |  |  | 160.9 |  |  | 165.7 |  |  | 151.2 |  |  | 256.1 |  |  | 121.4 |
Net income attributable to Alliant Energy common shareowners | 125.1 |  |  | 94.6 |  |  | 226.0 |  |  | 111.5 |  |  | 120.9 |  |  | 100.4 |  |  | 205.5 |  |  | 85.3 |
Earnings per weighted average common share attributable to Alliant Energy common shareowners | 0.53 |  |  | 0.40 |  |  | 0.94 |  |  | 0.46 |  |  | 0.52 |  |  | 0.43 |  |  | 0.87 |  |  | 0.36 |
IPL [Member] |
Components Of Selected Consolidated Quarterly Financial Data | Earnings per share data is not disclosed for IPL given Alliant Energy is the sole shareowner of all shares of IPL’s common stock outstanding during the periods presented.
| 2019 |  | 2018
| March 31 |  | June 30 |  | Sep. 30 |  | Dec. 31 |  | March 31 |  | June 30 |  | Sep. 30 |  | Dec. 31
| (in millions)
Revenues |  | $555.1 |  |  |  | $441.2 |  |  |  | $596.5 |  |  |  | $496.8 |  |  |  | $525.8 |  |  |  | $474.8 |  |  |  | $547.6 |  |  |  | $494.1 |
Operating income | 73.5 |  |  | 74.5 |  |  | 173.5 |  |  | 81.3 |  |  | 75.6 |  |  | 77.7 |  |  | 143.1 |  |  | 54.4 |
Net income | 55.9 |  |  | 47.5 |  |  | 143.7 |  |  | 47.2 |  |  | 49.3 |  |  | 54.2 |  |  | 129.1 |  |  | 41.6 |
Net income available for common stock | 53.3 |  |  | 45.0 |  |  | 141.1 |  |  | 44.7 |  |  | 46.7 |  |  | 51.7 |  |  | 126.5 |  |  | 39.1 |
WPL [Member] |
Components Of Selected Consolidated Quarterly Financial Data | Earnings per share data is not disclosed for WPL given Alliant Energy is the sole shareowner of all shares of WPL’s common stock outstanding during the periods presented.
| 2019 |  | 2018
| March 31 |  | June 30 |  | Sep. 30 |  | Dec. 31 |  | March 31 |  | June 30 |  | Sep. 30 |  | Dec. 31
| (in millions)
Revenues |  | $415.2 |  |  |  | $326.1 |  |  |  | $372.1 |  |  |  | $362.3 |  |  |  | $381.7 |  |  |  | $330.8 |  |  |  | $370.7 |  |  |  | $369.4 |
Operating income | 98.1 |  |  | 67.0 |  |  | 108.3 |  |  | 73.8 |  |  | 84.0 |  |  | 63.4 |  |  | 104.2 |  |  | 61.3 |
Net income | 65.7 |  |  | 42.0 |  |  | 75.5 |  |  | 49.8 |  |  | 54.0 |  |  | 39.8 |  |  | 76.3 |  |  | 38.0 |

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- Definition Tabular disclosure of quarterly financial data. Includes, but is not limited to, financial information for fiscal quarters, cumulative effect of a change in accounting principle and earnings per share data. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 270 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=118952077&loc=d3e1280-108306 + Details
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