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Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified | Dec. 31, 2013 | Dec. 31, 2012
--- | --- | ---
Other, accum depr. | $ 5.6 | $ 5.6
Non-regulated Generation, accum. depr. | 40.0 | 31.0
Alliant Energy Corporate Services, Inc. and other, accum. depr. | 214.2 | 200.2
Common stock, par value (in dollars per share) | $ 0.01 | $ 0.01
Common stock, shares authorized (in shares) | 240,000,000 | 240,000,000
Common stock, shares outstanding (in shares) | 110,943,669 | 110,987,400
Shares in deferred compensation trust (in shares) | 227,469 | 216,030
Shares in deferred compensation trust, weighted average cost per share (in dollars per share) | $ 35.25 | $ 33.61
IPL [Member] |  |
Other, accum depr. | 4.1 | 4.1
Common stock, par value (in dollars per share) | $ 2.50 | $ 2.50
Common stock, shares authorized (in shares) | 24,000,000 | 24,000,000
Common stock, shares outstanding (in shares) | 13,370,788 | 13,370,788
WPL [Member] |  |
Leased Sheboygan Falls Energy Facility, accum. depr. | 52.9 | 46.7
Other, accum depr. | $ 1.5 | $ 1.5
Common stock, par value (in dollars per share) | $ 5 | $ 5
Common stock, shares authorized (in shares) | 18,000,000 | 18,000,000
Common stock, shares outstanding (in shares) | 13,236,601 | 13,236,601

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