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Common Equity (Tables) | 12 Months Ended
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Dec. 31, 2014
Schedule of Common Equity [Line Items] |
Common Stock Activity | A summary of Alliant Energy’s common stock activity was as follows:
| 2014 |  | 2013 |  | 2012
Shares outstanding, January 1 | 110,943,669 |  |  | 110,987,400 |  |  | 111,018,821 |
Equity-based compensation plans (Note 12(b)) | 35,547 |  |  | (23,374 | ) |  | 20,195 |
Other | (43,536 | ) |  | (20,357 | ) |  | (51,616 | )
Shares outstanding, December 31 | 110,935,680 |  |  | 110,943,669 |  |  | 110,987,400 |
Schedule of Restricted Net Assets of Subsidiaries | As of December 31, the amount of net assets of IPL and WPL that were not available to be transferred to their parent company, Alliant Energy, in the form of loans, advances or cash dividends without the consent of IPL’s and WPL’s regulatory authorities was as follows (in billions):
| 2014 |  | 2013
IPL |  | $1.3 |  |  |  | $1.2 |
WPL | 1.6 |  |  | 1.5 |
Capital Transactions with Subsidiaries | IPL, WPL and Resources paid common stock dividends and repayments of capital to their parent company, Alliant Energy, as follows (in millions):
| IPL |  | WPL |  | Resources
| 2014 |  | 2013 |  | 2012 |  | 2014 |  | 2013 |  | 2012 |  | 2014 |  | 2013 |  | 2012
Common stock dividends |  | $140.0 |  |  |  | $128.1 |  |  |  | $122.9 |  |  |  | $118.7 |  |  |  | $116.3 |  |  |  | $112.0 |  |  |  | $— |  |  |  | $— |  |  |  | $— |
Repayments of capital | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 50.0 |  |  | 95.0 |  |  | — |
Total distributions from common equity |  | $140.0 |  |  |  | $128.1 |  |  |  | $122.9 |  |  |  | $118.7 |  |  |  | $116.3 |  |  |  | $112.0 |  |  |  | $50.0 |  |  |  | $95.0 |  |  |  | $— |
Schedule of Capital Contributions | IPL, WPL and Corporate Services received capital contributions from their parent company, Alliant Energy, as follows (in millions):
| 2014 |  | 2013 |  | 2012
IPL |  | $90.0 |  |  |  | $120.0 |  |  |  | $110.0 |
WPL | — |  |  | — |  |  | 90.0 |
Corporate Services | — |  |  | — |  |  | 30.0 |
IPL [Member] |
Schedule of Common Equity [Line Items] |
Schedule of Restricted Net Assets of Subsidiaries | As of December 31, the amount of net assets of IPL and WPL that were not available to be transferred to their parent company, Alliant Energy, in the form of loans, advances or cash dividends without the consent of IPL’s and WPL’s regulatory authorities was as follows (in billions):
| 2014 |  | 2013
IPL |  | $1.3 |  |  |  | $1.2 |
WPL | 1.6 |  |  | 1.5 |
Capital Transactions with Subsidiaries | IPL, WPL and Resources paid common stock dividends and repayments of capital to their parent company, Alliant Energy, as follows (in millions):
| IPL |  | WPL |  | Resources
| 2014 |  | 2013 |  | 2012 |  | 2014 |  | 2013 |  | 2012 |  | 2014 |  | 2013 |  | 2012
Common stock dividends |  | $140.0 |  |  |  | $128.1 |  |  |  | $122.9 |  |  |  | $118.7 |  |  |  | $116.3 |  |  |  | $112.0 |  |  |  | $— |  |  |  | $— |  |  |  | $— |
Repayments of capital | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 50.0 |  |  | 95.0 |  |  | — |
Total distributions from common equity |  | $140.0 |  |  |  | $128.1 |  |  |  | $122.9 |  |  |  | $118.7 |  |  |  | $116.3 |  |  |  | $112.0 |  |  |  | $50.0 |  |  |  | $95.0 |  |  |  | $— |
Schedule of Capital Contributions | IPL, WPL and Corporate Services received capital contributions from their parent company, Alliant Energy, as follows (in millions):
| 2014 |  | 2013 |  | 2012
IPL |  | $90.0 |  |  |  | $120.0 |  |  |  | $110.0 |
WPL | — |  |  | — |  |  | 90.0 |
Corporate Services | — |  |  | — |  |  | 30.0 |
WPL [Member] |
Schedule of Common Equity [Line Items] |
Schedule of Restricted Net Assets of Subsidiaries | As of December 31, the amount of net assets of IPL and WPL that were not available to be transferred to their parent company, Alliant Energy, in the form of loans, advances or cash dividends without the consent of IPL’s and WPL’s regulatory authorities was as follows (in billions):
| 2014 |  | 2013
IPL |  | $1.3 |  |  |  | $1.2 |
WPL | 1.6 |  |  | 1.5 |
Capital Transactions with Subsidiaries | IPL, WPL and Resources paid common stock dividends and repayments of capital to their parent company, Alliant Energy, as follows (in millions):
| IPL |  | WPL |  | Resources
| 2014 |  | 2013 |  | 2012 |  | 2014 |  | 2013 |  | 2012 |  | 2014 |  | 2013 |  | 2012
Common stock dividends |  | $140.0 |  |  |  | $128.1 |  |  |  | $122.9 |  |  |  | $118.7 |  |  |  | $116.3 |  |  |  | $112.0 |  |  |  | $— |  |  |  | $— |  |  |  | $— |
Repayments of capital | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 50.0 |  |  | 95.0 |  |  | — |
Total distributions from common equity |  | $140.0 |  |  |  | $128.1 |  |  |  | $122.9 |  |  |  | $118.7 |  |  |  | $116.3 |  |  |  | $112.0 |  |  |  | $50.0 |  |  |  | $95.0 |  |  |  | $— |
Schedule of Capital Contributions | IPL, WPL and Corporate Services received capital contributions from their parent company, Alliant Energy, as follows (in millions):
| 2014 |  | 2013 |  | 2012
IPL |  | $90.0 |  |  |  | $120.0 |  |  |  | $110.0 |
WPL | — |  |  | — |  |  | 90.0 |
Corporate Services | — |  |  | — |  |  | 30.0 |

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