Loans and Allowance for Loan Losses - Summary of Activity in Allowance for Loan Losses (Parenthetical) (Detail) - USD ($)		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018	Mar. 31, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Cumulative charges of loans and loans process of foreclosure		$ 54,560,000	[1]	$ 52,711,000	[1]	$ 49,495,000
Allowance for loan losses - ending balance		57,548,000	[2],[3]	46,093,000	[2],[3]	$ 36,395,000	$ 46,093,000
Net charge-offs	[4]	58,362,000		$ 37,688,000
Strategic Partnership [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - ending balance		0
Net charge-offs		0
Medallion Bank [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Cumulative charges of loans and loans process of foreclosure		$ 279,188,000

[1] Includes financed sales of this collateral to third parties that are reported separately from the loan portfolio, and that are conducted by Medallion Bank of $3,535 and $8,163 as of December 31, 2020 and 2019.

[2] As of December 31, 2020, the general reserves previously recorded for the Company’s medallion loan portfolio had been reversed as all loans had been deemed impaired and written down to collateral value.

[3] As of December 31, 2020, there was no allowance for loan losses and net charge-offs related to the strategic partnership loans.

[4] As of December 31, 2020, cumulative charge-offs of loans and loan collateral in process of foreclosure in the medallion loan portfolio were $279,188, some of which represents collection opportunities for the Company.