v3.19.3
Document and Entity Information - shares
9 Months Ended
Sep. 30, 2019
Nov. 01, 2019
Cover [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 30, 2019  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q3  
Entity Registrant Name Apellis Pharmaceuticals, Inc.  
Entity Central Index Key 0001492422  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity File Number 001-38276  
Entity Tax Identification Number 27-1537290  
Entity Address, Address Line One 6400 Westwind Way  
Entity Address, Address Line Two Suite A  
Entity Address, City or Town Crestwood  
Entity Address, State or Province KY  
Entity Address, Postal Zip Code 40014  
City Area Code (502)  
Local Phone Number 241-4114  
Entity Common Stock, Shares Outstanding   63,888,238
Entity Incorporation, State or Country Code DE  
Entity Interactive Data Current Yes  
Document Quarterly Report true  
Document Transition Report false  
Security 12b Title Common Stock  
Trading Symbol APLS  
Security Exchange Name NASDAQ