XML 90 R58.htm IDEA: XBRL DOCUMENT v2.4.0.6
Stock options (Details) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Weighted average fair value of options granted (in dollars per share) $ 2.32 $ 1.61 $ 3.04
Expected life (years) 5 years   8 years
Expected volatility factor 69.00%   90.00%
Expected dividends 0.00% 0.00% 0.00%
Minimum [Member]
     
Risk-free interest rate 0.65% 0.90% 2.50%
Expected life (years)   5 years  
Expected volatility factor   68.00%  
Maximum [Member]
     
Risk-free interest rate 0.74% 2.80% 3.20%
Expected life (years)   8 years  
Expected volatility factor   74.00%