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Redeemable Preferred Stock (Tables) | 12 Months Ended
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Dec. 31, 2014
Class of Stock [Line Items] |
Schedule of Carrying Value Of Cumulative Preferred Stock | Information related to the carrying value of IPL’s cumulative preferred stock at December 31 was as follows:
Liquidation Preference/Stated Value |  | Shares Authorized |  | Shares Outstanding |  | Series |  | 2014 |  | 2013
|  |  |  |  |  |  |  | (in millions)
$25 |  | 16,000,000 |  | 8,000,000 |  | 5.1% |  |  | $200.0 |  |  |  | $200.0 |
IPL [Member] |
Class of Stock [Line Items] |
Schedule of Carrying Value Of Cumulative Preferred Stock | Information related to the carrying value of IPL’s cumulative preferred stock at December 31 was as follows:
Liquidation Preference/Stated Value |  | Shares Authorized |  | Shares Outstanding |  | Series |  | 2014 |  | 2013
|  |  |  |  |  |  |  | (in millions)
$25 |  | 16,000,000 |  | 8,000,000 |  | 5.1% |  |  | $200.0 |  |  |  | $200.0 |

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