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Stock options and warrants (Schedule of Nonvested Awards) (Details) (USD $)
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12 Months Ended | |||
|---|---|---|---|---|
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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Stock Incentive Plan [Member]
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| Nonvested Shares Underlying Options | ||||
| Beginning balance | 508,435 | |||
| Granted | 525,603 | |||
| Vested | (824,400) | |||
| Forfeited | (9,192) | (24,476) | (9,510) | (1,078) |
| Ending balance | 200,446 | 508,435 | ||
| Weighted Average Exercise Price | ||||
| Beginning balance | $ 3.70 | |||
| Granted | $ 2.06 | |||
| Vested | 2.85 | |||
| Forfeited | $ 2.63 | |||
| Ending balance | $ 2.95 | $ 3.70 | ||
| Weighted Average Grant Date Fair Value | ||||
| Beginning balance | $ 3.07 | |||
| Granted | $ 1.75 | |||
| Vested | $ 2.38 | |||
| Forfeited | $ 2.21 | |||
| Ending balance | $ 2.48 | $ 3.07 | ||
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Nonqualified [Member]
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| Nonvested Shares Underlying Options | ||||
| Beginning balance | 8,333 | |||
| Granted | ||||
| Vested | (8,333) | |||
| Forfeited | ||||
| Ending balance | ||||
| Weighted Average Exercise Price | ||||
| Beginning balance | $ 3.42 | |||
| Granted | ||||
| Vested | 3.42 | |||
| Forfeited | ||||
| Ending balance | ||||
| Weighted Average Grant Date Fair Value | ||||
| Beginning balance | $ 2.84 | |||
| Granted | ||||
| Vested | $ 2.84 | |||
| Forfeited | ||||
| Ending balance | ||||