v3.26.3
Cover Page - shares
9 Months Ended
Sep. 30, 2026
Oct. 23, 2026
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Sep. 30, 2026  
Document Transition Report false  
Entity File Number 000-14656  
Entity Registrant Name REPLIGEN CORP  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 04-2729386  
Entity Address, State or Province MA  
Entity Address, Address Line One 41 Seyon Street, Bldg. 1, Suite 100  
Entity Address, City or Town Waltham  
Entity Address, Postal Zip Code 02453  
Local Phone Number 250-0111  
City Area Code 781  
Title of 12(b) Security Common Stock  
Trading Symbol RGEN  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Smaller reporting company false  
Emerging growth company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   63,923,738
Amendment Flag false  
Document Fiscal Period Focus Q3  
Document Fiscal Year Focus 2026  
Current Fiscal Year End Date --12-31  
Entity Central Index Key 0000730272