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Convertible Notes - Additional Information (Details) - Convertible notes (Notes)
$ / shares in Units, $ in Thousands
12 Months Ended
Feb. 03, 2015
USD ($)
$ / shares
Dec. 31, 2019
USD ($)
$ / shares
shares
Dec. 31, 2018
$ / shares
Dec. 31, 2017
$ / shares
Feb. 03, 2015
CNY (¥)
Debt Instrument [Line Items]          
Debt instrument, face amount $ 80,000        
Debt instrument, interest rate 3.50%       3.50%
Debt instrument, maturity date Feb. 03, 2020        
Debt Instrument, frequency of periodic payment semiannually        
Debt instrument, initial conversion price | $ / shares $ 23.03 $ 23.03 $ 23.03 $ 23.03  
Debt Instrument, initial conversion rate 43.4216        
Debt Instrument, repurchase price as a percentage of principal amount 100.00%        
Debt issuance costs | ¥         ¥ 0
Number of ADS that each ordinary share represents 2        
Portion of debt to be converted $ 10,000        
Amount of convertible notes converted $ 1,000 $ 21,090      
Stock issued during period, shares, conversion of convertible securities | shares   457,881      
American Depositary Shares          
Debt Instrument [Line Items]          
Stock issued during period, shares, conversion of convertible securities | shares   915,762