Segment Reporting - Schedule of Segment Data (Detail) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended
	Jun. 30, 2022		Mar. 31, 2022	Jun. 30, 2021		Mar. 31, 2021	Jun. 30, 2022		Jun. 30, 2021		Dec. 31, 2021
Segment Reporting Disclosure [Line Items]
Total interest income (loss)	$ 47,111			$ 37,375			$ 90,414		$ 74,455
Total interest expense	8,230			7,884			15,605		16,292
Net interest income (loss)	38,881			29,491			74,809		58,163
Provision (benefit) for loan losses	7,759			(682)			10,999		2,336
Net interest income (loss) after loss provision	31,122			30,173			63,810		55,827
Sponsorship and race winnings	0			4,345			0		6,818
Race team related expenses	0			(2,674)			0		(4,796)
Other income (expense), net	(11,455)			(13,724)			(27,958)		(26,781)
Income before income taxes	19,667			18,120			35,852		31,068
Net income (loss) before taxes	19,667			18,120			35,852		31,068
Income tax (provision) benefit	(4,856)			(6,528)			(9,687)		(10,406)
Net income (loss) after taxes/net increase (decrease) on net assets resulting from operations	14,811		$ 11,353	11,592		$ 9,071	26,165		20,662
Net income (loss) after taxes	14,811						26,165
Balance Sheet Data
Total loans, net	1,675,469			1,293,621			1,675,469		1,293,621		$ 1,438,758
total loans net	1,675,469						1,675,469
Total assets	2,112,131			1,739,747			2,112,131		1,739,747		$ 1,873,057
Total funds borrowed	$ 1,696,005			$ 1,382,109			$ 1,696,005		$ 1,382,109
Selected Financial Ratios
Return on average assets	2.63%			2.43%			2.37%		2.08%
Return on average stockholders' equity	18.11%			12.90%			15.93%		11.09%
Interest yield	11.00%			11.17%			11.04%		11.50%
Net interest margin	9.07%			8.84%			9.15%		9.01%
Reserve coverage	3.41%			3.50%			3.41%		3.50%
Delinquency status	0.25%	[1]		0.22%	[1]		0.25%	[2]	0.22%	[1]
Charge-off (recovery) ratio	0.18%	[3]		3.28%	[4]		0.26%	[4]	2.15%
RPAC [Member]
Segment Reporting Disclosure [Line Items]
Total interest income (loss)				$ 0					$ 0
Total interest expense				34					75
Net interest income (loss)				(34)					(75)
Provision (benefit) for loan losses				0					0
Net interest income (loss) after loss provision				(34)					(75)
Sponsorship and race winnings				4,345					6,818
Race team related expenses				(2,674)					(4,796)
Other income (expense), net				(1,862)					(3,623)
Income before income taxes				(225)					(1,676)
Income tax (provision) benefit				57					421
Net income (loss) after taxes/net increase (decrease) on net assets resulting from operations				(168)					(1,255)
Balance Sheet Data
Total loans, net				0					0
Total assets				31,877					31,877
Total funds borrowed				$ 8,016					$ 8,016
Selected Financial Ratios
Return on average assets				(1.05%)					(7.72%)
Return on average stockholders' equity				(39.70%)					(244.87%)
Operating Segments [Member] | Consumer Lending [Member] | Recreation [Member]
Segment Reporting Disclosure [Line Items]
Total interest income (loss)	$ 33,514			$ 28,886			$ 64,650		$ 56,328
Total interest expense	4,096			2,863			7,697		5,657
Net interest income (loss)	29,418			26,023			56,953		50,671
Provision (benefit) for loan losses	6,674			1,017			8,354		4,630
Net interest income (loss) after loss provision	22,744			25,006			48,599		46,041
Sponsorship and race winnings				0					0
Race team related expenses				0					0
Other income (expense), net	(7,551)			(7,455)			(14,371)		(12,918)
Income before income taxes	15,193			17,551			34,228		33,123
Income tax (provision) benefit	(3,567)			(4,519)			(9,248)		(8,529)
Net income (loss) after taxes/net increase (decrease) on net assets resulting from operations	11,626			13,032			24,980		24,594
Balance Sheet Data
Total loans, net	1,058,898			855,900			1,058,898		855,900
Total assets	1,072,356			868,709			1,072,356		868,709
Total funds borrowed	$ 861,083			$ 712,777			$ 861,083		$ 712,777
Selected Financial Ratios
Return on average assets	4.53%			6.24%			5.04%		6.06%
Return on average stockholders' equity	25.52%			31.19%			27.27%		30.32%
Interest yield	13.27%			14.03%			13.29%		14.18%
Net interest margin	11.65%			12.64%			11.71%		12.76%
Reserve coverage	3.44%			3.42%			3.44%		3.42%
Delinquency status	0.36%	[1]		0.32%	[1]		0.36%	[2]	0.32%	[1]
Charge-off (recovery) ratio	0.43%	[3]		(0.44%)	[4]		0.44%	[4]	0.12%
Operating Segments [Member] | Consumer Lending [Member] | Home Improvement [Member]
Segment Reporting Disclosure [Line Items]
Total interest income (loss)	$ 10,587			$ 8,228			$ 20,288		$ 16,146
Total interest expense	1,625			1,143			2,967		2,351
Net interest income (loss)	8,962			7,085			17,321		13,795
Provision (benefit) for loan losses	1,697			756			2,902		1,206
Net interest income (loss) after loss provision	7,265			6,329			14,419		12,589
Sponsorship and race winnings				0					0
Race team related expenses				0					0
Other income (expense), net	(3,210)			(2,638)			(6,106)		(4,552)
Income before income taxes	4,055			3,691			8,313		8,037
Income tax (provision) benefit	(975)			(951)			(2,246)		(2,070)
Net income (loss) after taxes/net increase (decrease) on net assets resulting from operations	3,080			2,740			6,067		5,967
Balance Sheet Data
Total loans, net	517,044			362,370			517,044		362,370
Total assets	521,931			375,189			521,931		375,189
Total funds borrowed	$ 419,101			$ 295,887			$ 419,101		$ 295,887
Selected Financial Ratios
Return on average assets	2.49%			3.04%			2.56%		3.39%
Return on average stockholders' equity	14.02%			15.19%			13.87%		16.96%
Interest yield	8.65%			9.48%			8.72%		9.56%
Net interest margin	7.33%			8.16%			7.45%		8.17%
Reserve coverage	1.75%			1.60%			1.75%		1.60%
Delinquency status	0.07%	[1]		0.02%	[1]		0.07%	[2]	0.02%	[1]
Charge-off (recovery) ratio	0.58%	[3]		0.26%	[4]		0.62%	[4]	0.99%
Operating Segments [Member] | Commercial Lending [Member]
Segment Reporting Disclosure [Line Items]
Total interest income (loss)	$ 2,278			$ 1,383			$ 4,208		$ 2,865
Total interest expense	785			716			1,507		1,288
Net interest income (loss)	1,493			667			2,701		1,577
Provision (benefit) for loan losses	1,879			0			3,134		0
Net interest income (loss) after loss provision	(386)			667			(433)		1,577
Sponsorship and race winnings				0					0
Race team related expenses				0					0
Other income (expense), net	3,263			(69)			1,932		(529)
Income before income taxes	2,877			598			1,499		1,048
Income tax (provision) benefit	(817)			(150)			(405)		(263)
Net income (loss) after taxes/net increase (decrease) on net assets resulting from operations	2,060			448			1,094		785
Balance Sheet Data
Total loans, net	94,208			66,236			94,208		66,236
Total assets	103,643			90,563			103,643		90,563
Total funds borrowed	$ 83,223			$ 72,450			$ 83,223		$ 72,450
Selected Financial Ratios
Return on average assets	8.06%			2.36%			2.15%		1.95%
Return on average stockholders' equity	49.17%			11.78%			12.21%		9.77%
Interest yield	10.60%			9.16%			10.28%		9.66%
Net interest margin	6.95%			4.42%			6.60%		5.32%
Reserve coverage	2.81%			0.00%			2.81%		0.00%
Delinquency status	0.08%	[1]		0.11%	[1]		0.08%	[2]	0.11%	[1]
Charge-off (recovery) ratio	(0.00%)	[3]		0.00%	[4]		3.75%	[4]	0.00%
Operating Segments [Member] | Medallion Lending [Member]
Segment Reporting Disclosure [Line Items]
Total interest income (loss)	$ 231			$ (1,475)			$ 377		$ (1,544)
Total interest expense	140			2,524			293		3,894
Net interest income (loss)	91			(3,999)			84		(5,438)
Provision (benefit) for loan losses	(2,675)			(2,943)			(3,544)		(3,987)
Net interest income (loss) after loss provision	2,766			(1,056)			3,628		(1,451)
Sponsorship and race winnings				0					0
Race team related expenses				0					0
Other income (expense), net	(760)			(1,157)			(1,566)		(3,301)
Income before income taxes	2,006			(2,213)			2,062		(4,752)
Income tax (provision) benefit	(541)			556			(557)		1,193
Net income (loss) after taxes/net increase (decrease) on net assets resulting from operations	1,465			(1,657)			1,505		(3,559)
Balance Sheet Data
Total loans, net	4,726			5,764			4,726		5,764
Total assets	31,258			101,205			31,258		101,205
Total funds borrowed	$ 25,099			$ 80,959			$ 25,099		$ 80,959
Selected Financial Ratios
Return on average assets	17.05%			(6.10%)			5.86%		(6.29%)
Return on average stockholders' equity	95.49%			(30.51%)			30.74%		(31.44%)
Interest yield	19.61%			(70.71%)			16.07%		(30.90%)
Net interest margin	7.78%			(189.15%)			3.58%		(108.84%)
Reserve coverage	66.61%			65.11%			66.61%		65.11%
Delinquency status	0.00%	[1]		0.00%	[1]		0.00%	[2]	0.00%	[1]
Charge-off (recovery) ratio	(232.80%)	[3]		513.86%	[4]		(153.24%)	[4]	216.01%
Intersegment Eliminations [Member]
Segment Reporting Disclosure [Line Items]
Total interest income (loss)	$ 501			$ 353			$ 891		$ 660
Total interest expense	1,584			604			3,141		3,027
Net interest income (loss)	(1,083)			(251)			(2,250)		(2,367)
Provision (benefit) for loan losses	184			488			153		487
Net interest income (loss) after loss provision	(1,267)			(739)			(2,403)		(2,854)
Sponsorship and race winnings				0					0
Race team related expenses				0					0
Other income (expense), net	(3,197)			(543)			(7,847)		(1,858)
Income before income taxes	(4,464)			(1,282)			(10,250)		(4,712)
Income tax (provision) benefit	1,044			(1,521)			2,769		(1,158)
Net income (loss) after taxes/net increase (decrease) on net assets resulting from operations	(3,420)			(2,803)			(7,481)		(5,870)
Balance Sheet Data
Total loans, net	593			3,351			593		3,351
Total assets	382,943			272,204			382,943		272,204
Total funds borrowed	$ 307,499			$ 212,020			$ 307,499		$ 212,020
Selected Financial Ratios
Return on average assets	(3.56%)			(3.85%)			(4.24%)		(4.08%)
Return on average stockholders' equity	(20.01%)			(1.95%)			(24.85%)		(30.46%)

[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.