Cost of revenues - Schedule of Cost of Revenues (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Deferred Revenue Arrangement [Line Items]      
Cost of revenues $ 60,034 $ 55,755 $ 50,258
Bandwidth costs [Member]      
Deferred Revenue Arrangement [Line Items]      
Cost of revenues 37,218 $ 33,545 28,174
Content costs, including amortization [Member]      
Deferred Revenue Arrangement [Line Items]      
Cost of revenues 338 1,061
Payment handling fees [Member]      
Deferred Revenue Arrangement [Line Items]      
Cost of revenues 9,087 $ 11,305 12,097
Depreciation of servers and other equipment [Member]      
Deferred Revenue Arrangement [Line Items]      
Cost of revenues 4,873 5,102 3,801
Games revenue sharing costs and others [Member]      
Deferred Revenue Arrangement [Line Items]      
Cost of revenues $ 8,518 $ 5,803 $ 5,125