Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2013	Feb. 12, 2014	Jun. 28, 2013
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	RGEN
Entity Registrant Name	REPLIGEN CORP
Entity Central Index Key	0000730272
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		31,935,541
Entity Public Float			$ 262,149,000