Segment Reporting - Schedule of Segment Data (Detail) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended
	Jun. 30, 2023		Mar. 31, 2023	Jun. 30, 2022		Mar. 31, 2022	Jun. 30, 2023		Jun. 30, 2022		Dec. 31, 2022
Segment Reporting Disclosure [Line Items]
Total interest income	$ 61,726			$ 47,111			$ 117,568		$ 90,414
Total interest expense	15,035			8,230			27,275		15,605
Net interest income (loss)	46,691			38,881			90,293		74,809
Provision (benefit) for credit losses	8,476			7,759			12,514		10,999
Net interest income (loss) after loss provision	38,215			31,122			77,779		63,810
Other income (expense), net	(17,061)			(11,455)			(33,370)		(27,958)
Income before income taxes	21,154			19,667			44,409		35,852
Income tax (provision) benefit	(5,472)			(4,856)			(11,854)		(9,687)
Net income (loss) after taxes	15,682		$ 16,873	14,811		$ 11,353	32,555		26,165
Income attributable to the non-controlling interest	1,512			1,511			3,024		3,024
Total net income attributable to Medallion Financial Corp.	14,170			13,300			29,531		23,141
Balance Sheet Data
Total loans	2,082,027						2,082,027				$ 1,853,108
Loans	2,156,998			1,734,621			2,156,998		1,734,621		1,916,953
Total assets	2,519,137			2,112,131			2,519,137		2,112,131		$ 2,259,879
Total funds borrowed	$ 2,066,607			$ 1,696,005			$ 2,066,607		$ 1,696,005
Selected Financial Ratios
Return on average assets	2.60%			2.93%			2.79%		2.68%
Return on average equity	16.52%			16.33%			17.49%		14.57%
Return on average stockholders' equity	18.24%			18.11%			19.45%		15.93%
Interest yield	11.59%			10.64%			11.01%		10.68%
Net interest margin, gross	8.48%			8.78%			8.45%		8.84%
Net interest margin, net of allowance	8.77%			9.07%			8.75%		9.15%
Reserve coverage	3.48%			3.41%			3.48%		3.41%
Delinquency status	0.29%	[1]		0.25%	[2]		0.29%	[3]	0.25%	[4]
Charge-off (recovery) ratio	0.74%	[5]		(0.17%)	[6]		1.51%	[7]	0.26%	[8]
Operating Segments [Member] | Consumer Lending [Member] | Recreation [Member]
Segment Reporting Disclosure [Line Items]
Total interest income	$ 41,109			$ 33,514			$ 79,008		$ 64,650
Total interest expense	7,580			4,096			13,484		7,697
Net interest income (loss)	33,529			29,418			65,524		56,953
Provision (benefit) for credit losses	10,135			6,674			17,886		8,354
Net interest income (loss) after loss provision	23,394			22,744			47,638		48,599
Other income (expense), net	(8,444)			(7,551)			(16,247)		(14,371)
Income before income taxes	14,950			15,193			31,391		34,228
Income tax (provision) benefit	(3,867)			(3,567)			(8,380)		(9,248)
Net income (loss) after taxes	11,083			11,626			23,011		24,980
Balance Sheet Data
Total loans	1,331,114			1,096,670			1,331,114		1,096,670
Total assets	1,294,925			1,072,356			1,294,925		1,072,356
Total funds borrowed	$ 1,062,309			$ 861,083			$ 1,062,309		$ 861,083
Selected Financial Ratios
Return on average assets	3.59%			4.53%			3.84%		5.04%
Return on average equity	22.94%			25.52%			24.13%		27.27%
Interest yield	13.03%			12.83%			12.93%		12.85%
Net interest margin, gross	10.63%			11.26%			10.72%		11.32%
Net interest margin, net of allowance	11.08%			11.65%			11.18%		11.71%
Reserve coverage	4.07%			3.44%			4.07%		3.44%
Delinquency status	0.39%	[1]		0.36%	[2]		0.39%	[3]	0.36%	[4]
Charge-off (recovery) ratio	1.86%	[5]		0.56%	[6]		2.57%	[7]	0.60%	[8]
Operating Segments [Member] | Consumer Lending [Member] | Home Improvement [Member]
Segment Reporting Disclosure [Line Items]
Total interest income	$ 15,292			$ 10,587			$ 28,941		$ 20,288
Total interest expense	4,194			1,626			7,473		2,967
Net interest income (loss)	11,098			8,961			21,468		17,321
Provision (benefit) for credit losses	3,739			1,697			6,820		2,902
Net interest income (loss) after loss provision	7,359			7,264			14,648		14,419
Other income (expense), net	(4,386)			(3,210)			(8,379)		(6,106)
Income before income taxes	2,973			4,054			6,269		8,313
Income tax (provision) benefit	(769)			(975)			(1,674)		(2,246)
Net income (loss) after taxes	2,204			3,079			4,595		6,067
Balance Sheet Data
Total loans	728,468			526,278			728,468		526,278
Total assets	718,383			521,931			718,383		521,931
Total funds borrowed	$ 589,335			$ 419,102			$ 589,335		$ 419,102
Selected Financial Ratios
Return on average assets	1.28%			2.49%			1.39%		2.56%
Return on average equity	8.19%			14.03%			8.76%		13.87%
Interest yield	8.79%			8.51%			8.66%		8.57%
Net interest margin, gross	6.38%			7.20%			6.43%		7.32%
Net interest margin, net of allowance	6.53%			7.33%			6.57%		7.45%
Reserve coverage	2.26%			1.75%			2.26%		1.75%
Delinquency status	0.16%	[1]		0.07%	[2]		0.16%	[3]	0.07%	[4]
Charge-off (recovery) ratio	1.12%	[5]		0.42%	[6]		0.97%	[7]	0.43%	[8]
Operating Segments [Member] | Commercial Lending [Member]
Segment Reporting Disclosure [Line Items]
Total interest income	$ 2,814			$ 2,278			$ 5,515		$ 4,208
Total interest expense	852			785			1,661		1,507
Net interest income (loss)	1,962			1,493			3,854		2,701
Provision (benefit) for credit losses	(113)			1,879			214		3,134
Net interest income (loss) after loss provision	2,075			(386)			3,640		(433)
Other income (expense), net	(804)			3,263			(953)		1,932
Income before income taxes	1,271			2,877			2,687		1,499
Income tax (provision) benefit	(329)			(816)			(718)		(405)
Net income (loss) after taxes	942			2,061			1,969		1,094
Balance Sheet Data
Total loans	92,637			96,928			92,637		96,928
Total assets	99,713			103,643			99,713		103,643
Total funds borrowed	$ 81,801			$ 83,224			$ 81,801		$ 83,224
Selected Financial Ratios
Return on average assets	3.76%			8.70%			3.94%		2.41%
Return on average equity	23.97%			49.03%			24.74%		12.20%
Interest yield	11.87%			10.41%			11.71%		10.13%
Net interest margin, gross	8.28%			6.82%			8.18%		6.50%
Net interest margin, net of allowance	8.54%			6.93%			8.43%		6.60%
Reserve coverage	2.72%			2.81%			2.72%		2.81%
Delinquency status	0.08%	[1]		0.08%	[2]		0.08%	[3]	0.08%	[4]
Charge-off (recovery) ratio	3.80%	[5]		(0.06%)	[6]		1.89%	[7]	3.70%	[8]
Operating Segments [Member] | Medallion Lending [Member]
Segment Reporting Disclosure [Line Items]
Total interest income	$ 787			$ 231			$ 1,097		$ 377
Total interest expense	46			140			113		293
Net interest income (loss)	741			91			984		84
Provision (benefit) for credit losses	(5,311)			(2,272)			(12,395)		(3,544)
Net interest income (loss) after loss provision	6,052			2,363			13,379		3,628
Other income (expense), net	561			(357)			153		(1,566)
Income before income taxes	6,613			2,006			13,532		2,062
Income tax (provision) benefit	(1,713)			(540)			(3,612)		(557)
Net income (loss) after taxes	4,900			1,466			9,920		1,505
Balance Sheet Data
Total loans	3,448			14,152			3,448		14,152
Total assets	18,724			31,258			18,724		31,258
Total funds borrowed	$ 15,360			$ 25,100			$ 15,360		$ 25,100
Selected Financial Ratios
Return on average assets	100.63%			17.04%			94.20%		5.85%
Return on average equity	641.63%			95.46%			590.25%		30.73%
Interest yield	83.55%			6.66%			28.80%		5.47%
Net interest margin, gross	78.67%			2.62%			25.84%		1.22%
Net interest margin, net of allowance	166.23%			7.88%			73.52%		3.61%
Reserve coverage	52.76%			66.61%			52.76%		66.61%
Delinquency status	0.00%	[1]		0.00%	[2]		0.00%	[3]	0.00%	[4]
Charge-off (recovery) ratio	(525.21%)	[5]		(77.17%)	[6]		(124.01%)	[7]	(51.66%)	[8]
Intersegment Eliminations [Member]
Segment Reporting Disclosure [Line Items]
Total interest income	$ 1,724			$ 501			$ 3,007		$ 891
Total interest expense	2,363			1,583			4,544		3,141
Net interest income (loss)	(639)			(1,082)			(1,537)		(2,250)
Provision (benefit) for credit losses	26			(219)			(11)		153
Net interest income (loss) after loss provision	(665)			(863)			(1,526)		(2,403)
Other income (expense), net	(3,988)			(3,600)			(7,944)		(7,847)
Income before income taxes	(4,653)			(4,463)			(9,470)		(10,250)
Income tax (provision) benefit	1,206			1,042			2,530		2,769
Net income (loss) after taxes	(3,447)			(3,421)			(6,940)		(7,481)
Balance Sheet Data
Total loans	1,331			593			1,331		593
Total assets	387,392			382,943			387,392		382,943
Total funds borrowed	$ 317,802			$ 307,496			$ 317,802		$ 307,496
Selected Financial Ratios
Return on average assets	(3.69%)			(3.56%)			(3.70%)		(4.24%)
Return on average equity	(22.83%)			(20.01%)			(23.24%)		(24.86%)

[1] Loans 90 days or more past due.

[2] Loans 90 days or more past due.

[3] Loans 90 days or more past due.

[4] Loans 90 days or more past due.

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

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

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

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