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Selected Consolidated Quarterly Financial Data (Unaudited) (Tables) | 12 Months Ended
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Dec. 31, 2017
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.
| 2017 |  | 2016
| March 31 |  | June 30 |  | Sep. 30 |  | Dec. 31 |  | March 31 |  | June 30 |  | Sep. 30 |  | Dec. 31
| (in millions, except per share data)
Operating revenues |  | $853.9 |  |  |  | $765.3 |  |  |  | $906.9 |  |  |  | $856.1 |  |  |  | $843.8 |  |  |  | $754.6 |  |  |  | $924.6 |  |  |  | $797.0 |
Operating income | 142.9 |  |  | 149.3 |  |  | 231.5 |  |  | 129.7 |  |  | 145.9 |  |  | 128.6 |  |  | 162.6 |  |  | 99.9 |
Amounts attributable to Alliant Energy common shareowners: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income from continuing operations, net of tax | 99.0 |  |  | 94.3 |  |  | 168.8 |  |  | 93.8 |  |  | 97.6 |  |  | 84.4 |  |  | 128.8 |  |  | 63.0 |
Income (loss) from discontinued operations, net of tax | 1.4 |  |  | — |  |  | — |  |  | — |  |  | (1.1 | ) |  | (0.5 | ) |  | (0.4 | ) |  | (0.3 | )
Net income | 100.4 |  |  | 94.3 |  |  | 168.8 |  |  | 93.8 |  |  | 96.5 |  |  | 83.9 |  |  | 128.4 |  |  | 62.7 |
Earnings per weighted average common share attributable to Alliant Energy common shareowners: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income from continuing operations, net of tax | 0.43 |  |  | 0.41 |  |  | 0.73 |  |  | 0.41 |  |  | 0.43 |  |  | 0.37 |  |  | 0.57 |  |  | 0.28 |
Income from discontinued operations, net of tax | 0.01 |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Net income | 0.44 |  |  | 0.41 |  |  | 0.73 |  |  | 0.41 |  |  | 0.43 |  |  | 0.37 |  |  | 0.57 |  |  | 0.28 |
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.
| 2017 |  | 2016
| March 31 |  | June 30 |  | Sep. 30 |  | Dec. 31 |  | March 31 |  | June 30 |  | Sep. 30 |  | Dec. 31
| (in millions)
Operating revenues |  | $450.5 |  |  |  | $420.2 |  |  |  | $527.4 |  |  |  | $472.2 |  |  |  | $458.7 |  |  |  | $411.0 |  |  |  | $516.2 |  |  |  | $434.5 |
Operating income | 49.6 |  |  | 66.3 |  |  | 131.8 |  |  | 49.2 |  |  | 62.0 |  |  | 48.0 |  |  | 125.9 |  |  | 34.9 |
Net income | 39.8 |  |  | 45.3 |  |  | 123.0 |  |  | 18.9 |  |  | 48.2 |  |  | 34.4 |  |  | 116.7 |  |  | 26.5 |
Earnings available for common stock | 37.2 |  |  | 42.8 |  |  | 120.4 |  |  | 16.4 |  |  | 45.6 |  |  | 31.9 |  |  | 114.1 |  |  | 24.0 |
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.
| 2017 |  | 2016
| March 31 |  | June 30 |  | Sep. 30 |  | Dec. 31 |  | March 31 |  | June 30 |  | Sep. 30 |  | Dec. 31
| (in millions)
Operating revenues |  | $393.1 |  |  |  | $334.8 |  |  |  | $370.2 |  |  |  | $374.7 |  |  |  | $375.6 |  |  |  | $334.3 |  |  |  | $397.0 |  |  |  | $352.2 |
Operating income | 86.0 |  |  | 73.7 |  |  | 90.7 |  |  | 72.8 |  |  | 78.8 |  |  | 75.0 |  |  | 115.0 |  |  | 58.2 |
Net income | 45.5 |  |  | 38.1 |  |  | 49.8 |  |  | 53.2 |  |  | 47.0 |  |  | 43.7 |  |  | 69.6 |  |  | 32.5 |
Earnings available for common stock | 45.5 |  |  | 38.1 |  |  | 49.8 |  |  | 53.2 |  |  | 46.5 |  |  | 43.2 |  |  | 69.0 |  |  | 31.7 |

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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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 270 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a)-(j) -URI http://asc.fasb.org/extlink&oid=68076893&loc=d3e1280-108306 + Details
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