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           Stock Plans and Stock-Based Compensation - Fair Value Of Option (Detail) (USD $) 
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        12 Months Ended | ||
|---|---|---|---|
| 
           Dec. 31, 2014 
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           Dec. 31, 2013 
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           Dec. 31, 2012 
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| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |||
| Expected stock price volatility | |||
| Risk free rate of interest | |||
| Maximum [Member] | |||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |||
| Exercise price | 
$ 9.21us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice / us-gaap_RangeAxis = us-gaap_MaximumMember  | 
        
$ 7.84us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice / us-gaap_RangeAxis = us-gaap_MaximumMember  | 
      |
| Expected stock price volatility | 
112.70%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate / us-gaap_RangeAxis = us-gaap_MaximumMember  | 
        
114.30%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate / us-gaap_RangeAxis = us-gaap_MaximumMember  | 
      |
| Risk free rate of interest | 
3.04%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / us-gaap_RangeAxis = us-gaap_MaximumMember  | 
        
2.23%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / us-gaap_RangeAxis = us-gaap_MaximumMember  | 
      |
| Expected life of options | 10 years | 10 years | |
| Minimum [Member] | |||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |||
| Exercise price | 
$ 1.71us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice / us-gaap_RangeAxis = us-gaap_MinimumMember  | 
        
$ 4.75us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice / us-gaap_RangeAxis = us-gaap_MinimumMember  | 
      |
| Expected stock price volatility | 
81.30%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate / us-gaap_RangeAxis = us-gaap_MinimumMember  | 
        
87.30%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate / us-gaap_RangeAxis = us-gaap_MinimumMember  | 
      |
| Risk free rate of interest | 
1.01%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / us-gaap_RangeAxis = us-gaap_MinimumMember  | 
        
0.16%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / us-gaap_RangeAxis = us-gaap_MinimumMember  | 
      |
| Expected life of options | 6 years | 2 years | |
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- Definition 
          Agreed-upon price for the exchange of the underlying asset relating to the share-based payment award. No definition available. 
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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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- 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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- 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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