Document and Entity Information - shares
9 Months Ended
Sep. 30, 2019
Oct. 23, 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  
Trading Symbol ACAD  
Entity Central Index Key 0001070494  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Common Stock, Shares Outstanding   154,025,462
Entity Current Reporting Status Yes  
Entity Shell Company false  
Entity File Number 000-50768  
Entity Tax Identification Number 06-1376651  
Entity Interactive Data Current Yes  
Document Quarterly Report true  
Document Transition Report false  
Entity Address, Address Line One 3611 Valley Centre Drive, Suite 300  
Entity Address, City or Town San Diego  
Entity Address, State or Province CA  
Entity Address, Postal Zip Code 92130  
City Area Code 858  
Local Phone Number 558-2871  
Entity Incorporation, State or Country Code DE  
Title of 12(b) Security Common Stock, par value $0.0001 per share  
Security Exchange Name NASDAQ