v2.4.0.6

Common Equity (Common Share Activity) (Details) | 12 Months Ended
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Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Common Stock Oustanding [Roll Forward] |  |  |  |  |  |
Shares outstanding, January 1 (in shares) | 111,018,821 |  | 110,893,901 |  | 110,656,498 |
Equity-based compensation plans (in shares) | 20,195 |  | 164,400 |  | 260,316 |
Other (in shares) | (51,616) | [1] | (39,480) | [1] | (22,913) | [1]
Shares outstanding, December 31 (in shares) | 110,987,400 |  | 111,018,821 |  | 110,893,901 |
[1] | Includes shares transferred from employees to Alliant Energy to satisfy tax withholding requirements in connection with the vesting of certain restricted stock under the equity-based compensation plans.

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