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Cover - USD ($)
12 Months Ended
Dec. 31, 2020
Feb. 28, 2021
Jun. 30, 2020
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Current Fiscal Year End Date --12-31    
Document Period End Date Dec. 31, 2020    
Document Transition Report false    
Entity File Number 001-35518    
Entity Registrant Name SUPERNUS PHARMACEUTICALS, INC.    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 20-2590184    
Entity Address, Address Line One 9715 Key West Avenue    
Entity Address, City or Town Rockville    
Entity Address, State or Province MD    
Entity Address, Postal Zip Code 20850    
City Area Code (301)    
Local Phone Number 838-2500    
Title of 12(b) Security Common Stock, $0.001 Par Value    
Entity Common Stock, Shares Outstanding   52,923,107  
Trading Symbol SUPN    
Security Exchange Name NASDAQ    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag true    
Entity Shell Company false    
Entity Public Float     $ 1,205,174,821
Documents Incorporated by Reference Certain portions of the registrant's definitive Proxy Statement for its 2021 Annual Meeting of Stockholders, which will be filed with the Securities and Exchange Commission not later than 120 days after the end of the registrant's 2020 fiscal year end, are incorporated by reference into Part III of this Annual Report on Form 10-K.    
Entity Central Index Key 0001356576    
Amendment Flag false    
Document Fiscal Year Focus 2020    
Document Fiscal Period Focus FY