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Stock Option and Purchase Plans (Details 1)
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12 Months Ended | ||
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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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| Summary of weighted-average assumptions | |||
| Dividend Yield | 0.00% | 0.00% | 0.00% |
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Maximum [Member]
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| Summary of weighted-average assumptions | |||
| Risk-free Interest Rate | 1.00% | 2.82% | 3.04% |
| Volatility Factor | 0.64% | 0.53% | 0.53% |
| Expected Life in Years | 8 years | 8 years | 8 years |
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Minimum [Member]
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| Summary of weighted-average assumptions | |||
| Risk-free Interest Rate | 0.89% | 1.55% | 2.33% |
| Volatility Factor | 0.52% | 0.52% | 0.41% |
| Expected Life in Years | 5 years | 7 years | 7 years |
| X | ||||||||||
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- Details
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| X | ||||||||||
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- Definition
The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The risk-free interest rate assumption that is used in valuing an option on its own shares. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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