Annual report pursuant to Section 13 and 15(d)

Stock Incentive Plan - Additional Information (Details)

v3.10.0.1
Stock Incentive Plan - Additional Information (Details)
$ / shares in Units, $ in Thousands
 12 Months Ended
Dec. 01, 2017
shares
Dec. 31, 2018
USD ($)
vote
$ / shares
shares
Dec. 31, 2017
USD ($)
$ / shares
shares
Dec. 31, 2016
USD ($)
$ / shares
shares
Dec. 31, 2011
Dec. 31, 2015
$ / shares
Dec. 31, 2010
$ / shares
shares
May 31, 2010
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Preferred stock, shares authorized (in shares)   5,000,000 5,000,000          
Preferred stock, par value (in dollars per share) | $ / shares   $ 0.0001 $ 0.0001          
Granted (in shares)   518,000 390,000 665,000        
Total intrinsic value of options exercised | $   $ 5,588 $ 808 $ 575        
Exercise of stock options, net (in shares)   909,000 401,000 321,000        
Exercised (in usd per share) | $ / shares   $ 7.367 $ 4.935 $ 3.286        
Exercise of stock options, net | $   $ 6,696 $ 1,977 $ 1,054        
Cash received from option exercises under all stock-based payment arrangements, net | $   $ 7,197 $ 1,977 $ 1,054        
Weighted average exercise price (in usd per share) | $ / shares   $ 8.050 $ 7.367 $ 7.300   $ 7.740    
Stock Options                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Options vesting period         5 years      
Ratable vesting percentage   33.33%            
Exercise term upon termination       90 days        
Weighted average exercise price (in usd per share) | $ / shares   $ 5.20 $ 2.93 $ 2.60        
Stock-based compensation expense | $   $ 1,258 $ 1,293 $ 1,462        
Non-vested stock options unrecognized compensation expense | $   $ 3,107            
Non-vested stock options unrecognized compensation expense, weighted-average period of recognition   2 years 1 month 18 days            
Stock Options | Minimum                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Options vesting period   3 years            
Class A Common Stock                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Common stock, shares authorized (in shares)   500,000,000 500,000,000          
Common stock, par value (in dollars per share) | $ / shares   $ 0.0001 $ 0.0001          
Number of votes per share | vote   1            
Class B Common Stock                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Common stock, shares authorized (in shares)   144,000,000 144,000,000          
Common stock, par value (in dollars per share) | $ / shares   $ 0.0001 $ 0.0001          
Number of votes per share | vote   5            
Common stock, shares issuable upon conversion (in shares)   1            
Preferred Stock                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Preferred stock, shares authorized (in shares)   5,000,000            
Preferred stock, par value (in dollars per share) | $ / shares   $ 0.0001            
2000 Stock Incentive Plan                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Common stock, par value (in dollars per share) | $ / shares             $ 0.0001  
Shares reserved for future issuance (in shares)             28,500,000  
2000 Stock Incentive Plan | Stock Options | Maximum                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Options vesting period   10 years            
2010 Stock Incentive Plan | Stock Options                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Shares available for grant (in shares)   6,833,000            
Options vesting period   10 years            
2010 Stock Incentive Plan | Class A Common Stock                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Shares reserved for future issuance (in shares)               10,000,000
Granted (in shares)   3,887,000            
2017 Employee Stock Purchase Plan | Stock Options                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Number of allocated shares (up to) (in shares) 200,000              
Discount from fair value of stock 5.00%              
Stock issued during period (in shares)   51,000