v3.10.0.1
Summary of significant accounting policies - Adoption of ASC 606 (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Jan. 01, 2018
Dec. 31, 2017
Adoption of ASC 606            
Accumulated deficit $ (130,346)   $ (130,346)     $ (131,967)
Accounts receivable, net 30,659   30,659   $ 25,079 26,148
Prepaid expenses and other current assets 9,013   9,013   6,539 6,369
Other assets 7,999   7,999   7,903 10,082
Deferred revenue, current 78,825   78,825   75,884 61,708
Deferred revenue, net of current portion 127,911   127,911   128,588 149,168
Non-controlling interests 2,181   2,181     1,212
Revenue 65,253 $ 53,655 183,013 $ 147,021    
Income tax expense 54 167 198 507    
Non-controlling interests 596 $ 210 1,447 $ 477    
Adjustment for adoption            
Adoption of ASC 606            
Accounts receivable, net         (1,069)  
Prepaid expenses and other current assets         170  
Other assets         (2,179)  
Deferred revenue, current         14,176  
Deferred revenue, net of current portion         (20,580)  
ASC 606 | As per ASC 605            
Adoption of ASC 606            
Accounts receivable, net 31,367   31,367     26,148
Prepaid expenses and other current assets 8,522   8,522     6,369
Other assets 10,213   10,213     10,082
Deferred revenue, current 79,738   79,738     61,708
Deferred revenue, net of current portion 140,040   140,040     $ 149,168
Non-controlling interests 228   228      
Revenue 63,884   176,168      
Income tax expense 258   638      
Non-controlling interests 270   (437)      
ASC 606 | Adjustment for adoption            
Adoption of ASC 606            
Accumulated deficit         3,257  
Accounts receivable, net (708)   (708)      
Prepaid expenses and other current assets 491   491      
Other assets (2,214)   (2,214)      
Deferred revenue, current (913)   (913)      
Deferred revenue, net of current portion (12,129)   (12,129)      
Non-controlling interests 1,953   1,953   $ 69  
Revenue 1,369   6,845      
Income tax expense (204)   (440)      
Non-controlling interests $ 326   $ 1,884