Stock Options (Details 2)
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1 Months Ended | 12 Months Ended | |||||||
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Oct. 31, 2013
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Apr. 30, 2013
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Oct. 31, 2012
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Apr. 30, 2012
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Oct. 31, 2011
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Apr. 30, 2011
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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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|
Stock Option [Line Items] | |||||||||
Expected volatility | 26.34% | 26.34% | 36.28% | 32.02% | 22.17% | 34.30% | 40.00% | 42.00% | |
Expected term (in years) | 6 months | 6 months | 6 months | 6 months | 6 months | 4 years | 4 years | 4 years 1 month 6 days | |
Risk-free interest rate | 0.15% | 0.15% | 0.35% | 0.12% | 0.20% | 0.80% | 0.80% | 1.50% |