Funds Borrowed - Summary of Key Attributes of Various Borrowing Arrangements with Lenders (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2020 USD ($)
Minimum [Member]
Notes Payable [Line Items]
Minimum monthly payments of pledged loan	$ 12,000
Maximum [Member]
Notes Payable [Line Items]
Minimum monthly payments of pledged loan	$ 85,000
Medallion Financial Corp [Member] | Notes Payable to Banks [Member]
Notes Payable [Line Items]
Description of variable rate basis	30 day LIBOR was 0.14%, 360 day LIBOR was 0.34%,
Medallion Chicago [Member] | Notes Payable to Banks [Member]
Notes Payable [Line Items]
Description of variable rate basis	One note has an interest rate of Prime, one note has an interest rate of Prime plus 0.50%, one note has a fixed interest rate of 3.75%, one note has an interest rate of LIBOR plus 3.75%, and the other interest rates on these borrowings are LIBOR plus 2%.
Debt Instrument interest rate, stated percentage	3.75%
30 Day LIBOR [Member] | Medallion Financial Corp [Member] | Notes Payable to Banks [Member]
Notes Payable [Line Items]
Debt Instrument interest rate, stated percentage	0.14%
360 Day LIBOR [Member] | Medallion Financial Corp [Member] | Notes Payable to Banks [Member]
Notes Payable [Line Items]
Debt Instrument interest rate, stated percentage	0.34%
Prime Rate [Member] | Medallion Financial Corp [Member] | Notes Payable to Banks [Member]
Notes Payable [Line Items]
Debt Instrument interest rate, stated percentage	3.25%
Prime Rate Plus [Member] | Medallion Chicago [Member] | Notes Payable to Banks [Member]
Notes Payable [Line Items]
Basis spread on variable rate	0.50%
Fixed Interest Rate [Member] | Medallion Chicago [Member] | Notes Payable to Banks [Member]
Notes Payable [Line Items]
Basis spread on variable rate	3.75%
LIBOR Rate [Member] | Medallion Chicago [Member] | Notes Payable to Banks [Member]
Notes Payable [Line Items]
Basis spread on variable rate	2.00%