v3.10.0.1
Segment and Geographic Information - Revenue and Total assets by segment (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
Revenue by segment          
Total segment revenue $ 97,423 $ 64,995 $ 189,711 $ 129,824  
Adjusted EBITDA (loss) by segment          
Total adjusted EBITDA (loss) (5,555) (1,497) (7,077) 2,411  
Net loss          
Net loss (18,347) (11,754) (33,218) (15,193)  
Adjustments          
Interest income 912 53 1,254 249  
Interest expense 27 1 54 1  
Foreign currency loss 825 1,031 1,220 1,031  
Depreciation and amortization expense 7,408 3,783 14,783 7,431  
Income tax benefit (3,565)   (4,793)    
Stock-based compensation expense 9,009 5,495 16,131 9,390  
Total adjustments $ 12,792 $ 10,257 $ 26,141 $ 17,604  
Segment profitability margin          
Total segment profitability margin (5.70%) (2.30%) (3.70%) 1.90%  
Total assets          
Total assets $ 825,464   $ 825,464   $ 482,062
Contract assets          
Accounts receivable, net 50,031   50,031   14,174
Contract assets 49,811   49,811   14,174
Contract liabilities          
Contract liabilities 30,862   30,862   7,024
Graduate Program Segment          
Revenue by segment          
Total segment revenue 81,209 $ 64,995 161,768 $ 129,824  
Adjusted EBITDA (loss) by segment          
Total adjusted EBITDA (loss) $ (5,905) $ (1,497) $ (6,179) $ 2,411  
Segment profitability margin          
Total segment profitability margin (6.10%) (2.30%) (3.20%) 1.90%  
Total assets          
Total assets $ 711,291   $ 711,291   359,597
Contract assets          
Accounts receivable, net 34,758   34,758   12,520
unbilled revenue 13,776   13,776   666
Contract liabilities          
Contract liabilities 22,829   22,829   2,523
Movement from deferred revenue          
Deferred revenue reclassified to revenue 0   2,500    
Contract Acquisition Costs          
Capitalized contract acquisition costs 200   300    
Amortization expense of capitalized contract cost 0   0    
Short Course Segment          
Revenue by segment          
Total segment revenue 16,214   27,943    
Adjusted EBITDA (loss) by segment          
Total adjusted EBITDA (loss) $ 350   $ (898)    
Segment profitability margin          
Total segment profitability margin 0.40%   (0.50%)    
Total assets          
Total assets $ 114,173   $ 114,173   122,465
Contract assets          
Accounts receivable, net 1,277   1,277   988
Contract liabilities          
Contract liabilities 8,033   8,033   $ 4,501
Movement from deferred revenue          
Deferred revenue reclassified to revenue $ 0   $ 4,500