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Document and Entity Information - USD ($)
$ in Billions
 12 Months Ended
Dec. 31, 2023
Feb. 20, 2024
Jun. 30, 2023
Cover [Abstract]      
Document Type 10-K/A    
Amendment Flag true    
Amendment Description Apellis Pharmaceuticals, Inc. (the “Company”) filed its Annual Report on Form 10-K for the fiscal year ended December 31, 2023 (the “Original Filing”) with the United States Securities and Exchange Commission (the “SEC”) on February 27, 2024. The Company is filing this Amendment No. 1 to the Original Filing (this “Amendment No. 1”) in order to correct (i) an inadvertent administrative error in the Critical Audit Matter section of the Report of Independent Registered Public Accounting Firm in Part II, Item 8 that resulted in an omission of text in the Original Filing and (ii) an inadvertent administrative error that resulted in the omission of the Report of Independent Registered Public Accounting Firm on internal controls over financial reporting, in Part II, Item 9A of the Original Filing.  In accordance with Rule 12b-15 (“Rule 12b-15”) under the Securities Exchange Act of 1934, as amended, the Original Filing is amended and restated in its entirety. However, there have been no changes made other than the corrections stated in the immediately preceding paragraph. In addition, the Company is including in this Amendment No. 1 new certifications of its principal executive officer and principal financial officer, as required by Rule 12b-15, as Exhibits 31.3, 31.4, 32.3 and 32.4, respectively, and a new consent from Deloitte & Touche LLP, the Company’s independent registered public accounting firm, as Exhibit 23.2. Except as described above, this Amendment No. 1 speaks as of the filing date of the Original Filing and does not amend or modify any other information contained in the Original Filing to reflect events that may have occurred subsequent to such filing date. Accordingly, this Amendment No. 1 should be read in conjunction with the Original Filing and the Company’s subsequent filings with the SEC.    
Document Period End Date Dec. 31, 2023    
Document Fiscal Year Focus 2023    
Document Fiscal Period Focus FY    
Trading Symbol APLS    
Entity Registrant Name APELLIS PHARMACEUTICALS, INC.    
Entity Central Index Key 0001492422    
Current Fiscal Year End Date --12-31    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Shell Company false    
Entity Common Stock, Shares Outstanding   120,581,749  
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Public Float     $ 10.7
Entity Current Reporting Status Yes    
Entity File Number 001-38276    
Entity Tax Identification Number 27-1537290    
Entity Address, Address Line One 100 Fifth Avenue    
Entity Address, City or Town Waltham    
Entity Address, State or Province MA    
Entity Address, Postal Zip Code 02451    
City Area Code 617    
Local Phone Number 977-5700    
Entity Interactive Data Current Yes    
Security 12b Title Common Stock, $0.0001 par value per share    
Security Exchange Name NASDAQ    
Entity Incorporation, State or Country Code DE    
Document Annual Report true    
Document Transition Report false    
Document Financial Statement Error Correction false    
ICFR Auditor Attestation Flag true    
Auditor Name Deloitte & Touche LLP    
Auditor Firm ID 34    
Auditor Location Boston, Massachusetts    
Documents Incorporated by Reference

The registrant intends to file a definitive proxy statement pursuant to Regulation 14A in connection with its 2024 Annual Meeting of Stockholders within 120 days of the end of the registrant’s fiscal year ended December 31, 2023. Portions of such proxy statement are incorporated by reference into Part III of this Annual Report on Form 10-K.