v3.19.1
Document and Entity Information - shares
3 Months Ended
Mar. 31, 2019
May 03, 2019
Document and Entity Information [Abstract]    
Entity Registrant Name ANAPTYSBIO INC  
Entity Central Index Key 0001370053  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Document Type 10-Q  
Document Period End Date Mar. 31, 2019  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q1  
Amendment Flag false  
Entity Common Stock, Shares Outstanding   27,023,725
Entity Emerging Growth Company false  
Entity Small Business false