Consolidated Statements of Income - USD ($)		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Interest and fees on loans	[1]		$ 95,080,000
Interest and dividends on investment securities	[1]		1,644,000
Medallion lease income	[1]		133,000
Interest income on investments	[1]		3,287,000
Interest income		$ 132,562,000
Dividends and interest income on short-term investments	[1]		0
Total interest income /total investment income	[1],[2]		100,836,000
Interest on deposits	[1]		14,230,000
Interest on short-term borrowings	[1]		4,441,000
Interest on long-term debt	[1]		6,145,000
Interest expense	[1]		3,551,000
Total interest expense		35,045,000	28,367,000	[1],[3]
Net interest income/net investment income		97,517,000	72,469,000	[1]
Provision for loan losses		47,386,000	59,008,000	[1]
Net interest income after provision for loan losses		50,131,000	13,461,000	[1]
Other income (loss)
Gain on deconsolidation of Trust III	[1]		25,325,000
Sponsorship and race winnings, net		18,742,000	14,368,000	[1]
Gain on the extinguishment of debt		4,145,000
Gain on sale of loans	[1]		4,946,000
Writedown of loan collateral in process of foreclosure	[1]		(2,188,000)
Impairment of equity investments	[1]		(939,000)
Other income	[1]		494,000
Total other income, net	[1]		42,006,000
Other expenses
Salaries and employee benefits	[1]		21,706,000
Race team related expenses		8,996,000	7,121,000	[1]
Professional fees	[1]		9,332,000
Collection costs	[1]		5,207,000
Loan servicing fees	[1]		3,470,000
Rent expense	[1]		2,040,000
Regulatory fees	[1]		1,703,000
Amortization of intangible assets		1,446,000	1,083,000	[1]
Travel, meals, and entertainment	[1]		1,448,000
Intangible asset impairment	[1]		5,615,000
Other expenses	[1],[4]		7,464,000
Total other expenses	[1],[5]		66,189,000
Income (loss) before income taxes/net investment loss before taxes		2,337,000	(10,722,000)	[1],[5]
Income tax (provision) benefit	[1]		(373,000)
Net income (loss) after taxes/net investment income (loss) after taxes	[1]		(11,095,000)
Net realized losses on investments	[1],[6]		(34,745,000)
Income tax benefit	[1]		8,426,000
Total net realized losses on investments	[1]		(26,319,000)
Net change in unrealized appreciation on Medallion Bank and other controlled subsidiaries	[1]		29,115,000
Net change in unrealized depreciation on investments other than securities	[1]		(1,915,000)
Net change in unrealized appreciation (depreciation) on investments	[1]		(4,403,000)
Income tax (provision) benefit	[1]		(8,122,000)
Net unrealized appreciation on investments	[1]		14,675,000
Net realized/unrealized gains (losses) on investments	[1]		(11,644,000)
Net income (loss) after taxes/net increase (decrease) on net assets resulting from operations		$ 1,996,000	(22,739,000)	[1]
Less: income attributable to the non-controlling interest	[1]		2,307,000
Total net income (loss) attributable to Medallion Financial Corp./net increase (decrease) on net assets resulting from operations	[1]		$ (25,046,000)
Basic net income (loss) per share		$ (0.07)	$ (1.03)	[1]	$ 0.01
Diluted net income (loss) per share		$ (0.07)	$ (1.03)	[1]	$ 0.01
Weighted average common shares outstanding
Basic		24,342,979	24,214,978	[1]	23,919,994
Diluted		24,342,979	24,214,978	[1]	24,053,307
Bank Holding Company Accounting [Member]
Interest and fees on loans		$ 130,167,000
Interest and dividends on investment securities		2,225,000
Medallion lease income		170,000
Total interest income /total investment income	[2]	132,562,000
Interest on deposits		22,521,000
Interest on short-term borrowings		3,242,000
Interest on long-term debt		9,282,000
Total interest expense	[3]	35,045,000
Net interest income/net investment income		97,517,000
Provision for loan losses		47,386,000
Net interest income after provision for loan losses		50,131,000
Other income (loss)
Sponsorship and race winnings, net		18,742,000
Gain on the extinguishment of debt		4,145,000
Writedown of loan collateral in process of foreclosure		(4,381,000)
Other income		1,881,000
Total other income, net		20,387,000
Other expenses
Salaries and employee benefits		24,971,000
Race team related expenses		8,996,000
Professional fees		7,402,000
Collection costs		6,638,000
Loan servicing fees		5,253,000
Rent expense		2,419,000
Regulatory fees		1,722,000
Amortization of intangible assets		1,446,000
Travel, meals, and entertainment		1,138,000
Other expenses	[4]	8,196,000
Total other expenses	[5]	68,181,000
Income (loss) before income taxes/net investment loss before taxes	[5]	2,337,000
Income tax (provision) benefit		(341,000)
Net income (loss) after taxes/net investment income (loss) after taxes		1,996,000
Net income (loss) after taxes/net increase (decrease) on net assets resulting from operations		1,996,000
Less: income attributable to the non-controlling interest		3,758,000
Total net income (loss) attributable to Medallion Financial Corp./net increase (decrease) on net assets resulting from operations		$ (1,762,000)
Basic net income (loss) per share		$ (0.07)
Diluted net income (loss) per share		$ (0.07)
Weighted average common shares outstanding
Basic		24,342,979
Diluted		24,342,979
Investment Company Accounting [Member]
Medallion lease income					$ 198,000
Interest income on investments					14,564,000
Dividends and interest income on short-term investments					878,000
Total interest income /total investment income	[2]				19,624,000
Interest expense					13,770,000
Total interest expense	[3]				13,770,000
Net interest income/net investment income					5,854,000
Net interest income after provision for loan losses					5,854,000
Other income (loss)
Other income					107,000
Total other income, net					107,000
Other expenses
Salaries and employee benefits					7,508,000
Professional fees					2,619,000
Collection costs					316,000
Rent expense					1,069,000
Travel, meals, and entertainment					750,000
Other expenses	[4]				1,548,000
Total other expenses	[5]				13,810,000
Income (loss) before income taxes/net investment loss before taxes	[5]				(7,849,000)
Income tax (provision) benefit					728,000
Net income (loss) after taxes/net investment income (loss) after taxes					(7,121,000)
Net realized losses on investments	[6]				(43,744,000)
Income tax benefit					15,955,000
Total net realized losses on investments					(27,789,000)
Net change in unrealized appreciation on Medallion Bank and other controlled subsidiaries					9,483,000
Net change in unrealized depreciation on investments other than securities					(2,060,000)
Net change in unrealized appreciation (depreciation) on investments					8,222,000
Income tax (provision) benefit					19,543,000
Net unrealized appreciation on investments					35,188,000
Net realized/unrealized gains (losses) on investments					7,399,000
Net income (loss) after taxes/net increase (decrease) on net assets resulting from operations					278,000
Total net income (loss) attributable to Medallion Financial Corp./net increase (decrease) on net assets resulting from operations					$ 278,000
Basic net income (loss) per share					$ 0.01
Diluted net income (loss) per share					$ 0.01
Weighted average common shares outstanding
Basic					23,919,994
Diluted					24,053,307
Controlled Subsidiary Investment [Member]
Dividend income from controlled subsidiaries	[1]		$ 28,000
Interest income	[1]		10,000
Controlled Subsidiary Investment [Member] | Investment Company Accounting [Member]
Dividend income from controlled subsidiaries					$ 1,278,000
Interest income					165,000
Affiliate Investment [Member]
Interest income	[1]		$ 654,000
Affiliate Investment [Member] | Investment Company Accounting [Member]
Interest income					$ 2,541,000

[1] Balance includes the nine months ended December 31, 2018 under Bank Holding Company Accounting and the three months ended March 31, 2018 under Investment Company Accounting.

[2] Included in interest and investment income is $834, $1,869 and $2,268 of paid in kind interest for the years ended December 31, 2019, 2018, and 2017.

[3] Average borrowings outstanding were $1,138,746, $1,198,124, and $334,022, and the related average borrowing costs were 3.08%, 2.37%, and 4.12% for the years ended December 31, 2019, 2018, and 2017.

[4] See Note 16 for the components of other expenses for the three months ended March 31, 2018 and the year ended December 31, 2017.

[5] Includes $256 and $870 of net revenues received from Medallion Bank for the years ended December 31, 2018 and 2017, primarily for expense reimbursements. See Notes 6 and 14 for additional information.

[6] There were no net losses on investment securities of affiliated issuers for the years ended December 31, 2018 and 2017.