| Document and Entity Information | May 28, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | PROTHENA CORP PUBLIC LTD CO |
| Entity Address, Country | IE |
| Amendment Flag | false |
| Entity Central Index Key | 0001559053 |
| Document Type | 8-K |
| Document Period End Date | May 28, 2021 |
| Entity Incorporation State Country Code | L2 |
| Entity File Number | 001-35676 |
| Entity Tax Identification Number | 98-1111119 |
| Entity Address, Address Line One | 77 Sir John Rogerson’s Quay, Block C |
| Entity Address, Address Line Two | Grand Canal Docklands |
| Entity Address, City or Town | Dublin 2 |
| Entity Address, Postal Zip Code | D02 VK60 |
| City Area Code | 1 |
| Local Phone Number | 236-2500 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Ordinary Shares, par value $0.01 per share |
| Trading Symbol | PRTA |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
