v3.8.0.1
Document and Entity Information - USD ($)
$ in Billions
12 Months Ended
Dec. 31, 2017
Jan. 31, 2018
Jun. 30, 2017
Document And Entity Information [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2017    
Document Fiscal Year Focus 2017    
Document Fiscal Period Focus FY    
Trading Symbol ACAD    
Entity Registrant Name ACADIA PHARMACEUTICALS INC    
Entity Central Index Key 0001070494    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer Yes    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Filer Category Large Accelerated Filer    
Entity Common Stock, Shares Outstanding   124,701,944  
Entity Public Float     $ 2.1