v3.8.0.1
Segment Information - Revenue and Total assets by segment (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Revenue by segment      
Total segment revenue $ 92,288 $ 64,829  
Adjusted EBITDA (loss) by segment      
Total adjusted EBITDA (loss) (1,522) 3,908  
Net loss      
Net loss (14,871) (3,439)  
Adjustments      
Interest income 342 196  
Interest expense 27    
Foreign currency loss 395    
Depreciation and amortization expense 7,375 3,648  
Income tax benefit (1,228)    
Stock-based compensation expense 7,122 3,895  
Total adjustments $ 13,349 $ 7,347  
Segment profitability margin      
Total segment profitability margin (1.60%) 6.00%  
Total assets      
Total assets $ 504,108 $ 482,062 $ 482,062
Contract assets      
Accounts receivable, net 40,290   14,174
Contract assets 40,246   14,174
Contract liabilities      
Contract liabilities 21,625   7,024
Graduate Program Segment      
Revenue by segment      
Total segment revenue 80,559 64,829  
Adjusted EBITDA (loss) by segment      
Total adjusted EBITDA (loss) $ (274) $ 3,908  
Segment profitability margin      
Total segment profitability margin (0.30%) 6.00%  
Total assets      
Total assets $ 372,405 $ 359,597  
Contract assets      
Accounts receivable, net 32,766   12,520
unbilled revenue 6,130   666
Contract liabilities      
Contract liabilities 12,931   2,523
Movement from deferred revenue      
Deferred revenue reclassified to revenue 2,500    
Contract Acquisition Costs      
Capitalized contract acquisition costs 100    
Amortization expense of capitalized contract cost 0    
Short Course Segment      
Revenue by segment      
Total segment revenue 11,729    
Adjusted EBITDA (loss) by segment      
Total adjusted EBITDA (loss) $ (1,248)    
Segment profitability margin      
Total segment profitability margin (1.30%)    
Total assets      
Total assets $ 131,703 $ 122,465  
Contract assets      
Accounts receivable, net 1,350   988
Contract liabilities      
Contract liabilities 8,694   $ 4,501
Movement from deferred revenue      
Deferred revenue reclassified to revenue $ 4,500