Loans and Allowance for Loan Losses - Summary of Activity in Allowance for Loan Losses (Parenthetical) (Detail) - USD ($) $ in Thousands		3 Months Ended
	Apr. 02, 2018	Mar. 31, 2020		Dec. 31, 2019		Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Losses [Line Items]
Cumulative charges of loans and loan collateral process of foreclosure		$ 46,817	[1]	$ 52,711	[1]	$ 49,808	$ 49,495
Percentage of Allowance		100.00%		100.00%
Bank reserves against future losses	$ 17,351
General reserve benefit	$ 7,266	$ 7,266
Medallion Bank [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Cumulative charges of loans and loan collateral process of foreclosure		243,428
Reserves against future losses		$ 2,469
Percentage of Allowance		5.00%
Percentage of total gross loans		2.07%
Financing Receivables, 90 Days Past Due [Member] | Medallion Bank [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserves against future losses		$ 2,469

[1] Includes financed sales of this collateral to third parties that are reported separately from the loan portfolio, and that are conducted by the Bank of $9,157 as of March 31, 2020 and $8,163 as of December 31, 2019.