| Cover | Jun. 12, 2019 |
| Cover [Abstract] | |
| Document Type | 8-K/A |
| Amendment Flag | true |
| Amendment Description | This Amendment No. 1 to Current Report on Form 8-K amends a Current Report on Form 8-K filed by Medifast, Inc. on June 13, 2019 (the “Report”), and is being filed solely to file a corrected version of Exhibit 3.1, an incorrect version of which was included in the Report. The incorrect version of Exhibit 3.1 filed with the Report contained errors in Article 2.3 and Article 2.5. A copy of the correct version is attached to this filing as Exhibit 3.1, which correct version properly indicates that the Board of Directors of the Company was declassified commencing with the Company’s annual meeting in 2015, and remains declassified. |
| Document Period End Date | Jun. 12, 2019 |
| Entity File Number | 001-31573 |
| Entity Registrant Name | MEDIFAST, INC. |
| Entity Central Index Key | 0000910329 |
| Entity Tax Identification Number | 13-3714405 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 100 International Drive |
| Entity Address, City or Town | Baltimore |
| Entity Address, State or Province | MD |
| Entity Address, Postal Zip Code | 21202 |
| City Area Code | 410 |
| Local Phone Number | 581-8042 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $0.001 per share |
| Trading Symbol | MED |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
