| Cover Page | Feb. 11, 2020 |
| Cover page. | |
| Document Type | 8-K |
| Document Period End Date | Feb. 11, 2020 |
| Entity Registrant Name | Supernus Pharmaceuticals, Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity Filer Name | 001-35518 |
| Entity Tax Identification Number | 20-2590184 |
| Entity Address, Address Line One | 1550 East Gude Drive |
| 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 per share |
| Trading Symbol | SUPN |
| Security Exchange Name | NASDAQ |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
| Entity Central Index Key | 0001356576 |
