Ordinary Shares - Additional Information (Detail) - USD ($)
$ in Thousands
 1 Months Ended 12 Months Ended
Nov. 30, 2014
Dec. 31, 2013
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Feb. 22, 2017
Jun. 30, 2016
Yun Chen Capital Cayman                
Class of Stock [Line Items]                
Percentage of the company owned by parent               47.40%
Ping An Insurance (Group) Company of China Ltd. [Member]                
Class of Stock [Line Items]                
Percentage of the company owned by parent     52.80%       6.50% 47.40%
Class A Ordinary Shares [Member]                
Class of Stock [Line Items]                
Number of ordinary shares outstanding   36,347,496 117,140,856 115,297,224        
Shares converted into Class A ordinary shares from Class B ordinary shares during the period     0 61,824,328 0 6,964,612    
Class A Ordinary Shares [Member] | Prior to the Completion of the IPO on December 11, 2013 [Member]                
Class of Stock [Line Items]                
Number of ordinary shares outstanding   27,354,496            
Class A Ordinary Shares [Member] | IPO [Member]                
Class of Stock [Line Items]                
Newly issued shares through offering   8,993,000            
Class B Ordinary Shares [Member]                
Class of Stock [Line Items]                
Number of ordinary shares outstanding   68,788,940            
Class B Ordinary Shares [Member] | Prior to the Completion of the IPO on December 11, 2013 [Member]                
Class of Stock [Line Items]                
Number of ordinary shares outstanding   68,788,940            
American Depositary Shares [Member] | IPO [Member]                
Class of Stock [Line Items]                
Newly issued shares through offering   8,993,000            
Proceeds from issuance of common stock   $ 142,590            
American Depositary Shares [Member] | Follow-on offering [Member]                
Class of Stock [Line Items]                
Newly issued shares through offering 2,424,801              
Proceeds from issuance of common stock $ 97,344