v2.4.0.6
Stock incentive plans (Details 2) (USD $)
In Thousands, except Per Share data, unless otherwise specified
 3 Months Ended 12 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Dec. 31, 2012
Recognized stock-based compensation expense      
Total stock-based compensation $ 602 $ 993  
Number of Options      
Outstanding at the beginning of the period (in shares) 5,045    
Granted (in shares) 466    
Exercised (in shares) (167)    
Cancelled/forfeited (in shares) (407)    
Outstanding at the end of the period (in shares) 4,937   5,045
Vested and expected to vest at the end of the period (in shares) 4,750    
Exercisable at the end of the period (in shares) 2,711    
Weighted Average Exercise Price      
Outstanding at the beginning of the period (in dollars per share) $ 6.50    
Granted (in dollars per share) $ 6.61    
Exercised (in dollars per share) $ 1.28    
Cancelled/forfeited (in dollars per share) $ 11.71    
Outstanding at the end of the period (in dollars per share) $ 6.26   $ 6.50
Vested and expected to vest at the end of the period (in dollars per share) $ 6.16    
Exercisable at the end of the period (in dollars per share) $ 3.74    
Weighted-Average Remaining Contract Life (years)      
Outstanding 6 years 7 months 2 days   6 years 5 months 8 days
Vested and expected to vest at the end of the period 6 years 5 months 26 days    
Exercisable at the end of the period 4 years 8 months 16 days    
Aggregate Intrinsic Value      
Outstanding at the beginning of the period 14,742    
Outstanding at the end of the period 8,960   14,742
Vested and expected to vest at the end of the period 8,956    
Exercisable at the end of the period 8,788    
Significant assumptions used for newly issued stock option grants      
Expected term 6 years 3 months    
Expected volatility (as a percent) 49.20%    
Risk free interest rate (as a percent) 1.00%    
Dividend yield (as a percent) 0.00%    
Network operations
      
Recognized stock-based compensation expense      
Total stock-based compensation 166 5  
Development and technology
      
Recognized stock-based compensation expense      
Total stock-based compensation (43) 200  
Selling and marketing
      
Recognized stock-based compensation expense      
Total stock-based compensation 118 210  
General and administrative
      
Recognized stock-based compensation expense      
Total stock-based compensation $ 361 $ 578