| Document and Entity Information | Aug. 03, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | CERUS CORP |
| Amendment Flag | false |
| Entity Central Index Key | 0001020214 |
| Document Type | 8-K |
| Document Period End Date | Aug. 3, 2021 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 000-21937 |
| Entity Tax Identification Number | 68-0262011 |
| Entity Address, Address Line One | 1220 Concord Ave |
| Entity Address, Address Line Two | Suite 600 |
| Entity Address, City or Town | Concord |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 94520 |
| City Area Code | (925) |
| Local Phone Number | 288-6000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $0.001 per share |
| Trading Symbol | CERS |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
