v3.7.0.1
Document and Entity Information - shares
3 Months Ended
Mar. 31, 2017
Apr. 21, 2017
Document Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Mar. 31, 2017  
Document Fiscal Year Focus 2017  
Document Fiscal Period Focus Q1  
Trading Symbol PRTA  
Entity Registrant Name Prothena Corp plc  
Entity Central Index Key 0001559053  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Entity Ordinary Shares Outstanding   38,020,181