Quarterly report pursuant to Section 13 or 15(d)

Stock Incentive Plan (Narrative) (Details)

v2.4.0.6
Stock Incentive Plan (Narrative) (Details) (USD $)
 3 Months Ended 3 Months Ended 35 Months Ended 3 Months Ended 12 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Dec. 31, 2010
Mar. 31, 2013
Class A Common Stock [Member]
Dec. 31, 2012
Class A Common Stock [Member]
Mar. 31, 2013
2000 Plan [Member]
Dec. 31, 2010
2000 Plan [Member]
Mar. 31, 2013
2010 Plan [Member]
Class A Common Stock [Member]
Dec. 31, 2010
2010 Plan [Member]
Class A Common Stock [Member]
Mar. 31, 2013
Stock Options [Member]
Dec. 31, 2010
Stock Options [Member]
Mar. 31, 2013
Stock Options [Member]
2010 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                        
Shares reserved for future issuance             28,500,000   10,000,000      
Common stock, par value (in usd per share)     $ 0.0001 $ 0.0001 $ 0.0001              
Options granted to date 0             964,144        
Shares available for grant                       9,083,292
Weighted-average remaining contractual life of all options expected to vest 8 years 1 month 10 days                      
Total intrinsic value of options exercised $ 1,321,076                      
Exercise of stock options (in shares) 247,956         247,956            
Options exercised average exercise price (in usd per share) $ 3.449         $ 3.449            
Proceeds from exercises of options 855,149 1,063,432                    
Options expiration period                   10 years    
Options vesting period                   5 years 5 years  
Options cliff vesting percentage                     20.00%  
Options ratable vesting percentage                   20.00% 5.00%  
Vesting frequency                     3 months  
Options postemployment exercisable period                   90 days    
Stock-based compensation expense 671,101 781,453                    
Non-vested stock options unrecognized compensation expense                   $ 6,028,929    
Non-vested stock options unrecognized compensation expense, weighted-average period of recognition                   2 years 11 months 23 days