| Document and Entity Information | Nov. 02, 2020 |
| Document And Entity Information [Line Items] | |
| Entity Registrant Name | MEDALLION FINANCIAL CORP |
| Amendment Flag | false |
| Entity Central Index Key | 0001000209 |
| Document Type | 8-K |
| Document Period End Date | Nov. 2, 2020 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-37747 |
| Entity Tax Identification Number | 04-3291176 |
| Entity Address, Address Line One | 437 Madison Avenue |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10022 |
| City Area Code | (212) |
| Local Phone Number | 328-2100 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Common Stock [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | Common Stock, par value $0.01 per share |
| Trading Symbol | MFIN |
| Security Exchange Name | NASDAQ |
| Nine Point Zero Zero Zero Percentage Senior Notes Due Twenty Twenty One [Member] | |
| Document And Entity Information [Line Items] | |
| Security 12b Title | 9.000% Senior Notes due 2021 |
| Trading Symbol | MFINL |
| Security Exchange Name | NASDAQ |
