v3.3.1.900
Stock-Based Compensation (Details)
$ / shares in Units, $ in Thousands
 3 Months Ended 12 Months Ended
Oct. 01, 2015
shares
Jul. 01, 2015
shares
Jun. 03, 2015
shares
Jun. 01, 2015
shares
Apr. 01, 2015
shares
Jan. 02, 2015
shares
Jan. 01, 2015
shares
Mar. 31, 2016
$ / shares
shares
Dec. 31, 2015
USD ($)
item
$ / shares
shares
Dec. 31, 2014
USD ($)
$ / shares
shares
Dec. 31, 2013
USD ($)
Jan. 01, 2016
shares
Jan. 30, 2014
shares
Stock-Based Compensation                          
Number of share-based employee compensation plans | item                 2        
Stock-based compensation expense included in the unaudited condensed consolidated statements of operations                          
Common stock reserved for issuance                 8,423,261        
Stock-based compensation expense | $                 $ 12,499 $ 7,527 $ 2,426    
Servicing and support                          
Stock-based compensation expense included in the unaudited condensed consolidated statements of operations                          
Stock-based compensation expense | $                 2,270 1,468 364    
Technology and content development                          
Stock-based compensation expense included in the unaudited condensed consolidated statements of operations                          
Stock-based compensation expense | $                 1,548 794 159    
Program marketing and sales                          
Stock-based compensation expense included in the unaudited condensed consolidated statements of operations                          
Stock-based compensation expense | $                 1,057 676 178    
General and administrative                          
Stock-based compensation expense included in the unaudited condensed consolidated statements of operations                          
Stock-based compensation expense | $                 $ 7,624 $ 4,589 $ 1,725    
Stock options                          
Stock-based compensation expense included in the unaudited condensed consolidated statements of operations                          
Option to purchase common stock, outstanding                 5,298,510 5,850,211      
Weighted average exercise price | $ / shares                 $ 8.07 $ 5.39      
Granted (in shares) 6,520 19,743 10,629 28,770 608,746 14,888 3,518   692,814        
Restricted Stock Units                          
Stock-based compensation expense included in the unaudited condensed consolidated statements of operations                          
Number of restricted stock units granted (in shares)                 585,765        
2014 Equity Incentive Plan                          
Stock-based compensation expense included in the unaudited condensed consolidated statements of operations                          
Option to purchase common stock, outstanding                 1,698,475        
Weighted average exercise price | $ / shares                 $ 17.03        
Shares authorized under the plan                 2,800,000        
Number of shares that may be added to the 2014 Plan                 5,943,348        
Period of annual automatic increase in the number of shares authorized                 10 years        
Percentage applied on total number of shares of common stock outstanding on previous calendar year for automatic inclusion in the plan                 5.00%        
Common stock reserved for issuance             2,036,503   1,904,743     2,288,820  
Common shares granted (in shares)               12,708          
2014 Equity Incentive Plan | Maximum                          
Stock-based compensation expense included in the unaudited condensed consolidated statements of operations                          
Number of options or stock awards available for grant under the Plan                 5,943,348        
2014 Equity Incentive Plan | Stock options                          
Stock-based compensation expense included in the unaudited condensed consolidated statements of operations                          
Granted (in shares)               3,617          
Exercise price (in dollars per share) | $ / shares               $ 27.98          
2014 Equity Incentive Plan | Restricted Stock Units                          
Stock-based compensation expense included in the unaudited condensed consolidated statements of operations                          
Number of restricted stock units granted (in shares)               8,177          
2008 Equity Incentive Plan                          
Stock-based compensation expense included in the unaudited condensed consolidated statements of operations                          
Number of options or stock awards available for grant under the Plan                         0
Option to purchase common stock, outstanding                 3,600,035        
Weighted average exercise price | $ / shares                 $ 3.84