| Document And Entity Information | Oct. 16, 2023 |
| Document Information [Line Items] | |
| Entity, Registrant Name | OMEROS CORPORATION |
| Document, Type | 8-K |
| Document, Period End Date | Oct. 16, 2023 |
| Entity, Incorporation, State or Country Code | WA |
| Entity, File Number | 001-34475 |
| Entity, Tax Identification Number | 91-1663741 |
| Entity, Address, Address Line One | 201 Elliott Avenue West |
| Entity, Address, City or Town | Seattle |
| Entity, Address, State or Province | WA |
| Entity, Address, Postal Zip Code | 98119 |
| City Area Code | 206 |
| Local Phone Number | 676-5000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock |
| Trading Symbol | OMER |
| Security Exchange Name | NASDAQ |
| Entity, Emerging Growth Company | false |
| Amendment Flag | false |
| Entity, Central Index Key | 0001285819 |
