v2.4.0.6
Document And Entity Information
9 Months Ended
Sep. 30, 2011
Nov. 01, 2011
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 30, 2011  
Document Fiscal Year Focus 2011  
Document Fiscal Period Focus Q3  
Entity Registrant Name ACHILLION PHARMACEUTICALS INC  
Entity Central Index Key 0001070336  
Current Fiscal Year End Date --12-31  
Entity Filer Category Smaller Reporting Company  
Entity Common Stock, Shares Outstanding   69,743,721