Segment Reporting - Schedule of Segment Data (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024		Mar. 31, 2023		Dec. 31, 2023
Segment Reporting Disclosure [Line Items]
Total interest income	$ 67,070		$ 55,843
Total interest expense	19,153		12,240
Net interest income (loss)	47,917		43,603
Provision (benefit) for credit losses	17,201		4,038
Net interest income (loss) after loss provision	30,716		39,565
Other income	5,403		2,083
Other expenses	(18,225)		(18,393)
Net income (loss) before taxes	17,894		23,255
Income tax (provision) benefit	(6,358)		(6,382)
Net income (loss) after taxes	11,536		16,873
Income attributable to the non-controlling interest	1,512		1,512
Total net income attributable to Medallion Financial Corp.	10,024		15,361
Balance Sheet Data
Total loans	2,144,599				$ 2,131,651
Loans	2,228,426		1,984,180		2,215,886
Total assets	2,618,762		2,351,670		$ 2,587,827
Total funds borrowed	$ 2,145,596		$ 1,916,390
Selected Financial Ratios
Return on average assets	1.80%		2.99%
Return on average stockholders' equity	11.65%		20.72%
Return on average equity	11.18%		18.50%
Interest yield	11.34%		10.78%
Net interest margin, gross	8.10%		8.42%
Net interest margin, net of allowance	8.39%		8.71%
Reserve coverage	3.76%		3.54%
Delinquency status	0.74%	[1]	0.24%	[2]
Charge-off (recovery) ratio	3.20%	[3]	2.35%	[4]
Operating Segments [Member] | Consumer Lending [Member] | Recreation [Member]
Segment Reporting Disclosure [Line Items]
Total interest income	$ 43,927		$ 37,899
Total interest expense	9,645		5,904
Net interest income (loss)	34,282		31,995
Provision (benefit) for credit losses	17,030		7,751
Net interest income (loss) after loss provision	17,252		24,244
Other income	250		0
Other expenses	(8,287)		(7,803)
Net income (loss) before taxes	9,215		16,441
Income tax (provision) benefit	(3,274)		(4,513)
Net income (loss) after taxes	5,941		11,928
Balance Sheet Data
Total loans	1,365,165		1,213,380
Total assets	1,322,761		1,179,965
Total funds borrowed	$ 1,083,760		$ 961,561
Selected Financial Ratios
Return on average assets	1.82%		4.14%
Return on average equity	11.44%		25.63%
Interest yield	13.17%		12.87%
Net interest margin, gross	10.28%		10.86%
Net interest margin, net of allowance	10.75%		11.33%
Reserve coverage	4.40%		4.12%
Delinquency status	0.48%	[1]	0.36%	[2]
Charge-off (recovery) ratio	4.36%	[3]	3.48%	[4]
Operating Segments [Member] | Consumer Lending [Member] | Home Improvement [Member]
Segment Reporting Disclosure [Line Items]
Total interest income	$ 17,447		$ 13,649
Total interest expense	5,634		3,279
Net interest income (loss)	11,813		10,370
Provision (benefit) for credit losses	898		3,081
Net interest income (loss) after loss provision	10,915		7,289
Other income	2		1
Other expenses	(4,114)		(3,994)
Net income (loss) before taxes	6,803		3,296
Income tax (provision) benefit	(2,417)		(905)
Net income (loss) after taxes	4,386		2,391
Balance Sheet Data
Total loans	752,262		669,642
Total assets	738,551		660,846
Total funds borrowed	$ 605,107		$ 538,527
Selected Financial Ratios
Return on average assets	2.38%		1.52%
Return on average equity	14.93%		9.37%
Interest yield	9.28%		8.54%
Net interest margin, gross	6.28%		6.49%
Net interest margin, net of allowance	6.45%		6.62%
Reserve coverage	2.38%		2.19%
Delinquency status	0.18%	[1]	0.07%	[2]
Charge-off (recovery) ratio	2.12%	[3]	0.82%	[4]
Operating Segments [Member] | Commercial Lending [Member]
Segment Reporting Disclosure [Line Items]
Total interest income	$ 3,645		$ 2,701
Total interest expense	1,098		809
Net interest income (loss)	2,547		1,892
Provision (benefit) for credit losses	216		327
Net interest income (loss) after loss provision	2,331		1,565
Other income	4,202		271
Other expenses	(985)		(420)
Net income (loss) before taxes	5,548		1,416
Income tax (provision) benefit	(1,971)		(389)
Net income (loss) after taxes	3,577		1,027
Balance Sheet Data
Total loans	106,570		95,329
Total assets	102,331		101,392
Total funds borrowed	$ 83,842		$ 82,625
Selected Financial Ratios
Return on average assets	13.50%		4.11%
Return on average equity	84.71%		25.39%
Interest yield	12.99%		11.53%
Net interest margin, gross	9.08%		8.08%
Net interest margin, net of allowance	9.43%		8.32%
Reserve coverage	4.11%		3.71%
Delinquency status	7.80%	[1]	0.08%	[2]
Charge-off (recovery) ratio	(0.07%)	[3]	(0.16%)	[4]
Operating Segments [Member] | Taxi Medallion Lending [Member]
Segment Reporting Disclosure [Line Items]
Total interest income	$ 140		$ 310
Total interest expense	28		67
Net interest income (loss)	112		243
Provision (benefit) for credit losses	(944)		(7,084)
Net interest income (loss) after loss provision	1,056		7,327
Other income	639		1,620
Other expenses	(743)		(2,027)
Net income (loss) before taxes	952		6,920
Income tax (provision) benefit	(338)		(1,899)
Net income (loss) after taxes	614		5,021
Balance Sheet Data
Total loans	3,560		4,059
Total assets	8,611		20,335
Total funds borrowed	$ 7,055		$ 16,571
Selected Financial Ratios
Return on average assets	23.68%		90.53%
Return on average equity	148.65%		558.90%
Interest yield	15.59%		11.78%
Net interest margin, gross	12.47%		9.23%
Net interest margin, net of allowance	21.57%		28.89%
Reserve coverage	42.19%		53.07%
Delinquency status	0.00%	[1]	0.00%	[2]
Charge-off (recovery) ratio	(101.47%)	[3]	29.84%	[4]
Intersegment Eliminations [Member]
Segment Reporting Disclosure [Line Items]
Total interest income	$ 1,911		$ 1,284
Total interest expense	2,748		2,181
Net interest income (loss)	(837)		(897)
Provision (benefit) for credit losses	1		(37)
Net interest income (loss) after loss provision	(838)		(860)
Other income	310		191
Other expenses	(4,096)		(4,149)
Net income (loss) before taxes	(4,624)		(4,818)
Income tax (provision) benefit	1,642		1,324
Net income (loss) after taxes	(2,982)		(3,494)
Balance Sheet Data
Total loans	869		1,770
Total assets	446,508		389,132
Total funds borrowed	$ 365,832		$ 317,106
Selected Financial Ratios
Return on average assets	(2.78%)		(3.79%)
Return on average equity	(17.47%)		(23.42%)

[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. (NM) Not meaningful.

[4] Negative balances indicate net recoveries for the period. (NM) Not meaningful.