Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2013	Mar. 11, 2014	Jun. 30, 2013
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2013
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	FY
Trading Symbol	OMER
Entity Registrant Name	OMEROS CORP
Entity Central Index Key	0001285819
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		30,397,366
Entity Public Float			$ 138,767,404