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Stock awards (Details 3) (USD $) | 12 Months Ended
--- | ---
Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Stock compensation plan [Member] |  |  |
Share-based compensation arrangement by share-based payment award [Line Items] |  |  |
Nonemployee director stock compensation plan, number of shares granted | 53,888 | 55,141 | 43,128
Nonemployee director stock compensation plan, fair value of shares granted | $ 1,100,000 | $ 1,100,000 | $ 849,000
Long-term incentive plan [Member] |  |  |
Share-based compensation arrangement by share-based payment award [Line Items] |  |  |
Common shares granted under a long-term incentive plan | 43,103 |  |
Fair value of common stock granted under a long-term incentive plan | $ 930,000 |  |

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- Definition Common shares granted under a long-term incentive plan. + References No definition available. + Details
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- Definition Fair value of common stock granted under a long-term incentive plan. + References No definition available. + Details
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- Definition Identification of the company's common stock (in shares) issued in the transaction in which equity securities were issued for nonemployee services. + References No definition available. + Details
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- Definition The fair value of the company's common stock issued in the transaction in which equity securities were issued for nonemployee services. + References No definition available. + Details
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- Details
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