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Condensed Consolidated Balance Sheets (Parenthetical) (USD $) | Mar. 31, 2014 | Dec. 31, 2013
--- | --- | ---
Common stock, par value | $ 0.01 | $ 0.01
Common stock, shares authorized (in shares) | 240,000,000 | 240,000,000
Common stock, shares outstanding (in shares) | 110,937,182 | 110,943,669
Shares in deferred compensation trust (in shares) | 224,076 | 227,469
Shares in deferred compensation trust, weighted average cost per share (in dollars per share) | $ 35.89 | $ 35.25
IPL [Member] |  |
Common stock, par value | $ 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] |  |
Common stock, par value | $ 5.00 | $ 5.00
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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