Segment Reporting - Schedule of Segment Data (Detail) - USD ($)	3 Months Ended								9 Months Ended
	Sep. 30, 2022		Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021		Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022		Sep. 30, 2021		Dec. 31, 2021
Segment Reporting Disclosure [Line Items]
Total interest income (loss)	$ 51,694,000				$ 41,497,000				$ 142,108,000		$ 115,953,000
Total interest expense	9,654,000				7,426,000				25,258,000		23,718,000
Net interest income (loss)	42,040,000				34,071,000				116,850,000		92,235,000
Provision (benefit) for loan losses	10,047,000				(337,000)				21,046,000		2,000,000
Net interest income (loss) after loss provision	31,993,000				34,408,000				95,804,000		90,235,000
Sponsorship and race winnings	0				3,335,000				0		10,153,000
Race team related expenses	0				(2,424,000)				0		(7,219,000)
Other income (expense), net	(19,640,000)				(12,428,000)				(47,600,000)		(39,210,000)
Income before income taxes	12,353,000				22,891,000				48,204,000		53,959,000
Net income (loss) before taxes	12,353,000				22,891,000				48,204,000		53,959,000
Income tax (provision) benefit	(3,205,000)				(6,167,000)				(12,892,000)		(16,573,000)
Net income (loss) after taxes/net increase (decrease) on net assets resulting from operations	9,148,000		$ 14,811,000	$ 11,353,000	16,724,000		$ 11,592,000	$ 9,071,000	35,312,000		37,386,000
Net income (loss) after taxes	9,148,000								35,312,000
Less: income attributable to the non-controlling interest	1,512,000				784,000				4,535,000		2,748,000
Total net income attributable to Medallion Financial Corp.	7,636,000				15,940,000				30,777,000		34,638,000
Balance Sheet Data
Total loans, net	1,793,975,000				1,372,233,000				1,793,975,000		1,372,233,000		$ 1,438,758,000
Total assets	2,199,541,000				1,805,234,000				2,199,541,000		1,805,234,000		$ 1,873,057,000
Total funds borrowed	$ 1,782,465,000				$ 1,424,142,000				$ 1,782,465,000		$ 1,424,142,000
Selected Financial Ratios
Return on average assets	1.68%				3.73%				2.33%		2.73%
Return on average equity	10.03%				20.02%				13.05%		15.61%
Return on average stockholders' equity	10.35%				24.38%						18.71%
Interest yield	10.97%				11.55%				11.03%		11.56%
Net interest margin	8.91%				9.48%				9.09%		9.19%
Reserve coverage	3.32%				3.34%				3.32%		3.34%
Delinquency status	0.33%	[1]			0.29%	[1]			0.33%	[2]	0.29%	[2]
Charge-off (recovery) ratio	1.75%	[3]			(0.38%)	[4]			0.81%	[4]	1.17%
RPAC [Member]
Segment Reporting Disclosure [Line Items]
Total interest income (loss)					$ 0						$ 0
Total interest expense					38,000						113,000
Net interest income (loss)					(38,000)						(113,000)
Provision (benefit) for loan losses					0						0
Net interest income (loss) after loss provision					(38,000)						(113,000)
Sponsorship and race winnings					3,335,000						10,153,000
Race team related expenses					(2,424,000)						(7,219,000)
Other income (expense), net					(2,066,000)						(5,689,000)
Income before income taxes					(1,193,000)						(2,868,000)
Income tax (provision) benefit					299,000						720,000
Net income (loss) after taxes/net increase (decrease) on net assets resulting from operations					(894,000)						(2,148,000)
Total net income attributable to Medallion Financial Corp.					(894,000)						(2,148,000)
Balance Sheet Data
Total loans, net					0						0
Total assets					30,969,000						30,969,000
Total funds borrowed					$ 8,054,000						$ 8,054,000
Selected Financial Ratios
Return on average assets					(11.28%)						(8.89%)
Return on average equity					(11.08%)						(386.73%)
Operating Segments [Member] | Consumer Lending [Member]
Balance Sheet Data
Total assets	$ 1,145,380,000								$ 1,145,380,000
Operating Segments [Member] | Consumer Lending [Member] | Recreation [Member]
Segment Reporting Disclosure [Line Items]
Total interest income (loss)	36,539,000				$ 30,529,000				101,189,000		$ 86,857,000
Total interest expense	5,003,000				2,305,000				12,700,000		7,962,000
Net interest income (loss)	31,536,000				28,224,000				88,489,000		78,895,000
Provision (benefit) for loan losses	7,182,000				916,000				15,536,000		5,546,000
Net interest income (loss) after loss provision	24,354,000				27,308,000				72,953,000		73,349,000
Sponsorship and race winnings					0						0
Race team related expenses					0						0
Other income (expense), net	(7,178,000)				(8,856,000)				(21,549,000)		(21,774,000)
Income before income taxes	17,176,000				18,452,000				51,404,000		51,575,000
Income tax (provision) benefit	(4,499,000)				(4,752,000)				(13,747,000)		(13,281,000)
Net income (loss) after taxes/net increase (decrease) on net assets resulting from operations	12,677,000				13,700,000				37,657,000		38,294,000
Total net income attributable to Medallion Financial Corp.	12,677,000				13,700,000				37,657,000		38,294,000
Balance Sheet Data
Total loans, net	1,131,051,000				902,234,000				1,131,051,000		902,234,000
Total assets	1,145,380,000				916,109,000				1,145,380,000		916,109,000
Total funds borrowed	$ 928,194,000				$ 712,474,000				$ 928,194,000		$ 712,474,000
Selected Financial Ratios
Return on average assets	4.54%				6.09%				4.86%		6.08%
Return on average equity	27.07%				30.46%				27.16%		30.39%
Interest yield	13.19%				13.78%				13.26%		14.05%
Net interest margin	11.38%				12.74%				11.60%		12.76%
Reserve coverage	3.48%				3.38%				3.48%		3.38%
Delinquency status	0.45%	[1]			0.34%	[1]			0.45%	[2]	0.34%	[2]
Charge-off (recovery) ratio	1.51%	[3]			(0.15%)	[4]			0.94%	[4]	0.22%
Operating Segments [Member] | Consumer Lending [Member] | Home Improvement [Member]
Segment Reporting Disclosure [Line Items]
Total interest income (loss)	$ 11,689,000				$ 8,586,000				$ 31,977,000		$ 24,732,000
Total interest expense	2,093,000				958,000				5,060,000		3,309,000
Net interest income (loss)	9,596,000				7,628,000				26,917,000		21,423,000
Provision (benefit) for loan losses	2,041,000				369,000				4,943,000		1,575,000
Net interest income (loss) after loss provision	7,555,000				7,259,000				21,974,000		19,848,000
Sponsorship and race winnings					0						0
Race team related expenses					0						0
Other income (expense), net	(3,163,000)				(3,437,000)				(9,269,000)		(7,989,000)
Income before income taxes	4,392,000				3,822,000				12,705,000		11,859,000
Income tax (provision) benefit	(1,152,000)				(951,000)				(3,398,000)		(3,054,000)
Net income (loss) after taxes/net increase (decrease) on net assets resulting from operations	3,240,000				2,871,000				9,307,000		8,805,000
Total net income attributable to Medallion Financial Corp.	3,240,000				2,871,000				9,307,000		8,805,000
Balance Sheet Data
Total loans, net	565,002,000				392,278,000				565,002,000		392,278,000
Total assets	569,603,000				405,439,000				569,603,000		405,439,000
Total funds borrowed	$ 461,595,000				$ 296,509,000				$ 461,595,000		$ 296,509,000
Selected Financial Ratios
Return on average assets	2.36%				2.89%				2.48%		3.20%
Return on average equity	14.06%				14.43%				13.91%		16.02%
Interest yield	8.57%				9.04%				8.67%		9.37%
Net interest margin	7.03%				8.03%				7.30%		8.11%
Reserve coverage	1.77%				1.63%				1.77%		1.63%
Delinquency status	0.08%	[1]			0.04%	[1]			0.08%	[2]	0.04%	[2]
Charge-off (recovery) ratio	0.78%	[3]			0.25%	[4]			0.57%	[4]	0.09%
Operating Segments [Member] | Commercial Lending [Member]
Segment Reporting Disclosure [Line Items]
Total interest income (loss)	$ 2,493,000				$ 2,055,000				$ 6,701,000		$ 4,920,000
Total interest expense	780,000				662,000				2,287,000		1,950,000
Net interest income (loss)	1,713,000				1,393,000				4,414,000		2,970,000
Provision (benefit) for loan losses	2,100,000				0				5,234,000		0
Net interest income (loss) after loss provision	(387,000)				1,393,000				(820,000)		2,970,000
Sponsorship and race winnings					0						0
Race team related expenses					0						0
Other income (expense), net	2,214,000				636,000				282,000		107,000
Income before income taxes	2,601,000				2,029,000				1,102,000		3,077,000
Income tax (provision) benefit	(700,000)				(510,000)				(295,000)		(773,000)
Net income (loss) after taxes/net increase (decrease) on net assets resulting from operations	1,901,000				1,519,000				807,000		2,304,000
Total net income attributable to Medallion Financial Corp.	(1,901,000)				1,519,000				(807,000)		2,304,000
Balance Sheet Data
Total loans, net	92,772,000				70,232,000				92,772,000		70,232,000
Total assets	102,367,000				92,257,000				102,367,000		92,257,000
Total funds borrowed	$ 82,956,000				$ 73,806,000				$ 82,956,000		$ 73,806,000
Selected Financial Ratios
Return on average assets	7.32%				6.60%				1.05%		3.68%
Return on average equity	(43.65%)				32.99%				(6.08%)		18.38%
Interest yield	10.82%				12.04%				10.55%		10.56%
Net interest margin	7.43%				8.16%				6.95%		6.37%
Reserve coverage	1.03%				0.00%				1.03%		0.00%
Delinquency status	0.08%	[1]			0.10%	[1]			0.08%	[2]	0.10%	[2]
Charge-off (recovery) ratio	(16.74%)	[3]			0.00%	[4]			8.49%	[4]	0.00%
Operating Segments [Member] | Medallion Lending [Member]
Segment Reporting Disclosure [Line Items]
Total interest income (loss)	$ 92,000				$ 1,000				$ 469,000		$ (1,543,000)
Total interest expense	133,000				2,009,000				426,000		5,903,000
Net interest income (loss)	41,000				(2,008,000)				43,000		(7,446,000)
Provision (benefit) for loan losses	(1,275,000)				(1,944,000)				(4,819,000)		(5,931,000)
Net interest income (loss) after loss provision	1,234,000				(64,000)				4,862,000		(1,515,000)
Sponsorship and race winnings					0						0
Race team related expenses					0						0
Other income (expense), net	(2,686,000)				2,073,000				(4,252,000)		(1,228,000)
Income before income taxes	1,452,000				2,009,000				610,000		(2,743,000)
Income tax (provision) benefit	(394,000)				(504,000)				(163,000)		689,000
Net income (loss) after taxes/net increase (decrease) on net assets resulting from operations	1,058,000				1,505,000				447,000		(2,054,000)
Total net income attributable to Medallion Financial Corp.	(1,058,000)				1,505,000				447,000		(2,054,000)
Balance Sheet Data
Total loans, net	4,377,000				5,538,000				4,377,000		5,538,000
Total assets	27,860,000				93,683,000				27,860,000		93,683,000
Total funds borrowed	$ 22,577,000				$ 74,941,000				$ 22,577,000		$ 74,941,000
Selected Financial Ratios
Return on average assets	13.00%				6.12%				1.30%		(2.52%)
Return on average equity	(74.61%)				30.62%				6.99%		(12.60%)
Interest yield	8.12%				0.09%				13.61%		(23.55%)
Net interest margin	3.62%				(139.64%)				1.25%		(113.66%)
Reserve coverage	68.68%				49.98%				68.68%		49.98%
Delinquency status	2.24%	[1]			5.42%	[1]			2.24%	[2]	5.42%	[2]
Charge-off (recovery) ratio	(127.68%)	[3]			(43.01%)	[4]			(145.36%)	[4]	143.94%
Intersegment Eliminations [Member]
Segment Reporting Disclosure [Line Items]
Total interest income (loss)	$ 881,000				$ 326,000				$ 1,772,000		$ 987,000
Total interest expense	1,645,000				1,454,000				4,785,000		4,481,000
Net interest income (loss)	(764,000)				(1,128,000)				(3,013,000)		(3,494,000)
Provision (benefit) for loan losses	1,000				322,000				152,000		810,000
Net interest income (loss) after loss provision	(763,000)				(1,450,000)				(3,165,000)		(4,304,000)
Sponsorship and race winnings					0						0
Race team related expenses					0						0
Other income (expense), net	(4,399,000)				(778,000)				(12,248,000)		(2,637,000)
Income before income taxes	(5,162,000)				(2,228,000)				(15,413,000)		(6,941,000)
Income tax (provision) benefit	1,352,000				251,000				4,121,000		(874,000)
Net income (loss) after taxes/net increase (decrease) on net assets resulting from operations	(3,810,000)				(1,977,000)				(11,292,000)		(7,815,000)
Total net income attributable to Medallion Financial Corp.	(3,810,000)				(1,977,000)				(11,292,000)		(7,815,000)
Balance Sheet Data
Total loans, net	773,000				1,951,000				773,000		1,951,000
Total assets	354,331,000				266,777,000				354,331,000		266,777,000
Total funds borrowed	$ 287,143,000				$ 258,358,000				$ 287,143,000		$ 258,358,000
Selected Financial Ratios
Return on average assets	(4.10%)				(2.65%)				4.24%		(3.68%)
Return on average equity	(24.41%)				(19.79%)				(25.15%)		(27.18%)

[1] Loans 90 days or more past due.

[2] Loans 90 days or more past due.

[3] Negative balances indicate net recoveries for the period.

[4] Negative balances indicate net recoveries for the period.