Loans and Allowance for Loan Losses - Summary of Activity in Allowance for Loan Losses (Parenthetical) (Detail) - USD ($)			3 Months Ended				6 Months Ended
		Apr. 02, 2018	Jun. 30, 2020		Jun. 30, 2019		Jun. 30, 2020		Jun. 30, 2019		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			$ 47,375,000	[1]	$ 52,368,000		$ 47,375,000	[1]	$ 52,368,000		$ 46,817,000	$ 52,711,000	[1]	$ 49,808,000	$ 49,495,000
Percentage of Allowance			100.00%				100.00%					100.00%
Bank reserves against future losses		$ 17,351,000
General reserve benefit		$ 11,555,000
Allowance for loan losses			$ 66,977,000	[2],[3]	40,670,000	[2],[3]	$ 66,977,000	[2],[3]	40,670,000	[2],[3]	$ 54,057,000	$ 46,093,000		$ 36,862,000	$ 36,395,000
Net charge-offs	[4]		4,021,000		11,363,000		12,598,000		24,239,000
Strategic Partnership [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses			0		0		0		0
Net charge-offs			0		$ 0		0		$ 0
Medallion Bank [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Cumulative charges of loans and loan collateral process of foreclosure			$ 245,058,000				245,058,000
Reserves against future losses							$ 2,025,000
Percentage of Allowance			3.00%				3.00%
Percentage of total gross loans							1.94%
Financing Receivables, 90 Days Past Due [Member] | Medallion Bank [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Reserves against future losses							$ 2,025,000

[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 $9,265 as of June 30, 2020 and $8,163 as of December 31, 2019.

[2] As of June 30, 2020, there was no allowance for loan loss and net charge-offs related to the strategic partnership loans.

[3] Includes $2,025 of a general reserve for the Company, for current and performing medallion loans under 90 days past due, as an additional buffer against future losses, representing 3% of the total allowance, and 1.94% of the medallion loans under 90 days past due as of June 30, 2020. This figure excludes $17,351 of a general reserve on loans at the Bank, which was netted against loan balances at consolidation on April 2, 2018. Subsequent to April 2, 2018, the Bank recorded a general reserve benefit of $11,555.

[4] As of June 30, 2020, cumulative net charge-offs of loans and loan collateral in process of foreclosure in the medallion loan portfolio were $245,058, representing collection opportunities for the Company.