Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Outstanding Warrants Valuation Assumption (Detail)

v2.4.0.8
Stockholders' Equity - Outstanding Warrants Valuation Assumption (Detail) (USD $)
6 Months Ended 12 Months Ended
Jun. 30, 2013
Dec. 31, 2012
August 2008 offering [Member]
   
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]    
Risk-free interest rate 0.10% 0.16%
Expected life (in years) 1 month 28 days 7 months 28 days
Dividend yield      
Volatility 62.00% 118.00%
Stock price $ 5.26 $ 4.21
October 2009 offering [Member]
   
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]    
Risk-free interest rate 0.36% 0.25%
Expected life (in years) 1 year 3 months 7 days 1 year 9 months 4 days
Dividend yield      
Volatility 63.00% 98.00%
Stock price $ 5.26 $ 4.21
March 2011 offering [Member]
   
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]    
Risk-free interest rate 0.66% 0.72%
Expected life (in years) 2 years 8 months 16 days 3 years 2 months 16 days
Dividend yield      
Volatility 95.00% 94.00%
Stock price $ 5.26 $ 4.21