Quarterly report pursuant to Section 13 or 15(d)

Shareholders' equity (Details)

v3.8.0.1
Shareholders' equity (Details) - USD ($)
$ / shares in Units, $ in Thousands
 9 Months Ended
Apr. 10, 2017
Mar. 27, 2017
Sep. 30, 2017
Stockholders' equity      
Proceeds from issuance of common stock     $ 103,167
Common stock      
Stockholders' equity      
Issuance of common stock (in shares)     136,201,338
Stock offering expenses     $ 4,774
Secondary Public Offering      
Stockholders' equity      
Issuance of shares represented by American Depositary Shares (in ADSs)   15,700,223  
Share price per ADS (in dollars per share)   $ 4.20  
Secondary Public Offering | Common stock      
Stockholders' equity      
Issuance of common stock (in shares)   94,201,338  
Proceeds from issuance of common stock   $ 61,397  
Stock offering expenses   $ 4,544  
Matrix Capital Management Company, LP      
Stockholders' equity      
Issuance of shares represented by American Depositary Shares (in ADSs) 7,000,000    
Share price per ADS (in dollars per share) $ 6.00    
Matrix Capital Management Company, LP | Common stock      
Stockholders' equity      
Issuance of common stock (in shares) 42,000,000    
Proceeds from issuance of common stock $ 41,770    
Stock offering expenses $ 230