Property and Equipment, Net (Tables)
 12 Months Ended
Dec. 31, 2017
Property, Plant and Equipment [Abstract]  
Summary of Property and Equipment

Property and equipment consist of the following:

 

     December 31,  
     2016      2017  
     RMB      RMB      US$  

At cost:

         

Electronic equipment

      234,360        301,783        46,383  

Office equipment

      1,024        1,361        209  

Motor vehicles

      3,418        2,855        439  

Software

      26,480        34,310        5,273  

Leasehold improvements

      42,364        40,408        6,211  
  

 

 

     

 

 

     

 

 

  
     307,646        380,717        58,515  

Less: Accumulated depreciation

      (173,072 )       (250,395 )       (38,485 ) 
  

 

 

     

 

 

     

 

 

  
     134,574        130,322        20,030