Quarterly report pursuant to Section 13 or 15(d)

Stock Incentive Plan (Narrative) (Details)

v2.4.0.8
Stock Incentive Plan (Narrative) (Details) (USD $)
 3 Months Ended 6 Months Ended 6 Months Ended 35 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Jun. 30, 2012
Dec. 31, 2010
Jun. 30, 2013
Class A Common Stock [Member]
Dec. 31, 2012
Class A Common Stock [Member]
Jun. 30, 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]
Jun. 30, 2013
Stock Options [Member]
Dec. 31, 2010
Stock Options [Member]
Jun. 30, 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     104,360             1,068,504        
Shares available for grant                           9,016,528
Weighted-average remaining contractual life of all options expected to vest     8 years 7 days                      
Total intrinsic value of options exercised     $ 1,942,087                      
Exercise of stock options (in shares)     364,666         364,666            
Options exercised average exercise price (in usd per share)     $ 3.427         $ 3.427            
Proceeds from exercises of options 394,603 735,839 1,249,752 1,799,271                    
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 664,759 892,607 1,335,860 1,674,060                    
Non-vested stock options unrecognized compensation expense                       $ 5,701,994    
Non-vested stock options unrecognized compensation expense, weighted-average period of recognition                       2 years 10 months 17 days