v3.8.0.1
Business Combination - Estimated fair values of the assets acquired and liabilities assumed (Details) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Jul. 01, 2017
Dec. 31, 2017
Dec. 31, 2016
Acquisition      
Common stock, par value (in dollars per share)   $ 0.001 $ 0.001
Goodwill   $ 71,988  
GetSmarter      
Acquisition      
Cash consideration $ 98,700    
Potential earn-out payment $ 20,000    
Common stock, par value (in dollars per share) $ 0.001    
Cash and Cash Equivalents $ 1,584    
Current assets 3,676    
Property and equipment, net 479    
Goodwill 68,172    
Current Liabilities (9,031)    
Non-Current Liabilities (10,894)    
Total $ 98,686    
Decrease in goodwill related to contingent consideration   $ 2,000  
GetSmarter | Minimum      
Acquisition      
Vesting period (in years) 2 years    
GetSmarter | Maximum      
Acquisition      
Vesting period (in years) 4 years    
Capitalized technology | GetSmarter      
Acquisition      
Amortizable intangible assets $ 2,800    
Capitalized content development | GetSmarter      
Acquisition      
Amortizable intangible assets 5,000    
University client relationships | GetSmarter      
Acquisition      
Amortizable intangible assets 28,000    
Trade names and domain names | GetSmarter      
Acquisition      
Amortizable intangible assets $ 8,900