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Common Equity (Tables) | 9 Months Ended
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Sep. 30, 2017
Stockholders' Equity Note [Abstract] |
Common Share Activity | A summary of Alliant Energy’s common stock activity was as follows:
Shares outstanding, January 1, 2017 | 227,673,654 |
At-the-market offering program | 3,074,931 |
Shareowner Direct Plan issuances | 496,437 |
Equity-based compensation plans (Note 9(b)) | 5,185 |
Other | (45,847 | )
Shares outstanding, September 30, 2017 | 231,204,360 |

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