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The Company - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Nov. 19, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Business Description [Line Items]        
Common stock shares sold 9,315,000      
Public offering price $ 18.00      
Net proceeds from initial public offering and concurrent private placement $ 171,800      
Underwriting discounts and commissions 11,700      
Offering expenses 4,100      
Common stock, aggregate purchase price $ 20,000 $ 0 $ 20,000 $ 0
Convertible preferred stock converted into shares of common stock 33,919,954 33,919,954    
FibroGen Europe [Member]        
Business Description [Line Items]        
Convertible preferred stock converted into shares of common stock 958,996 1