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Common Stock and Preferred Stock (Tables) | 6 Months Ended
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Jun. 30, 2013
Details on Preferred Stock | Details on preferred stock at June 30, 2013, June 30, 2012 and December 31, 2012 are shown below:
|  | June 30, |  |  | December 31, |
|  | 2013 |  |  | 2012 |  |  | 2012 |
Preferred Stock |  |  |  |  |  |  |  |  |  |  |  |
Unitil Energy Preferred Stock, Non-Redeemable, Non-Cumulative: |  |  |  |  |  |  |  |  |  |  |  |
6.00% Series, $100 Par Value, |  | $ | 0.2 |  |  | $ | 0.2 |  |  | $ | 0.2 |
Fitchburg Preferred Stock, Redeemable, Cumulative: |  |  |  |  |  |  |  |  |  |  |  |
5.125% Series, $100 Par Value |  |  | — |  |  |  | 0.8 |  |  |  | — |
8.00% Series, $100 Par Value |  |  | — |  |  |  | 1.0 |  |  |  | — |
Total Preferred Stock |  | $ | 0.2 |  |  | $ | 2.0 |  |  | $ | 0.2 |

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- Definition Preferred Stock Shares + References No definition available. + Details
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Namespace Prefix: | utl_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration