Segment Reporting - Schedule of Segment Data (Detail) - USD ($) $ in Thousands		3 Months Ended						9 Months Ended
		Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Segment Reporting Disclosure [Line Items]
Total interest income		$ 37,440			$ 34,640			$ 108,570	$ 96,698
Total interest expense		8,384			9,225			26,219	25,768
Net interest income		29,056			25,415			82,351	70,930
Provision for loan losses		39,749			8,337			73,231	36,851
Net interest income after provision for loan losses		(10,693)			17,078			9,120	34,079
Sponsorship and race winnings		8,962			7,940			15,161	16,008
Race team related expenses		(2,636)			(2,663)			(6,584)	(7,211)
Other income (expense), net		(24,047)			(14,755)			(65,479)	(42,615)
Income (loss) before income taxes		(28,414)			7,600			(47,782)	261
Income tax (provision) benefit		8,381			(165)			12,483	1,926
Net income (loss)		(20,033)	$ (2,265)	$ (13,001)	7,435	$ (6,643)	$ 1,395	(35,299)	2,187
Balance Sheet Data
Total loans, net		1,190,544			1,099,169			1,190,544	1,099,169	$ 1,114,762
Total assets		1,604,275			1,519,754			1,604,275	1,519,754	1,541,667
Total funds borrowed		$ 1,271,185			$ 1,187,115			$ 1,271,185	$ 1,187,115	1,169,593
Selected Financial Ratios
Return on average assets		(5.69%)			1.31%			(3.43%)	(0.12%)
Return on average equity		(29.77%)			6.81%			(17.02%)	(0.60%)
Interest yield		11.23%			11.87%			11.31%	11.68%
Net interest margin		8.72%			8.71%			8.58%	8.57%
Reserve coverage		7.07%			3.77%			7.07%	3.77%
Delinquency status	[1]	1.07%			0.73%			1.07%	0.73%
Charge-off ratio		5.36%			2.17%			3.30%	3.92%
RPAC [Member]
Segment Reporting Disclosure [Line Items]
Total interest expense		$ 42			$ 47			$ 122	$ 119
Net interest income		(42)			(47)			(122)	(119)
Net interest income after provision for loan losses		(42)			(47)			(122)	(119)
Sponsorship and race winnings		8,962			7,940			15,161	16,008
Race team related expenses		(2,636)			(2,663)			(6,584)	(7,211)
Other income (expense), net		(2,503)			(1,784)			(5,726)	(5,298)
Income (loss) before income taxes		3,781			3,446			2,729	3,380
Income tax (provision) benefit		(942)			(831)			(680)	(815)
Net income (loss)		2,839			2,615			2,049	2,565
Balance Sheet Data
Total assets		40,112			33,134			40,112	33,134	31,538
Total funds borrowed		$ 8,652			$ 7,758			$ 8,652	$ 7,758	7,794
Selected Financial Ratios
Return on average assets		31.97%			31.13%			8.27%	10.76%
Operating Segments [Member] | Consumer Lending [Member] | Recreation [Member]
Segment Reporting Disclosure [Line Items]
Total interest income		$ 28,962			$ 26,147			$ 82,525	$ 72,996
Total interest expense		3,476			3,578			10,268	9,541
Net interest income		25,486			22,569			72,257	63,455
Provision for loan losses		1,812			6,744			20,705	19,925
Net interest income after provision for loan losses		23,674			15,825			51,552	43,530
Other income (expense), net		(7,246)			(6,181)			(21,115)	(17,501)
Income (loss) before income taxes		16,428			9,644			30,437	26,029
Income tax (provision) benefit		(4,201)			(2,497)			(7,783)	(6,741)
Net income (loss)		12,227			7,147			22,654	19,288
Balance Sheet Data
Total loans, net		774,956			690,466			774,956	690,466	695,257
Total assets		788,459			702,541			788,459	702,541	707,377
Total funds borrowed		$ 628,528			$ 559,995			$ 628,528	$ 559,995	563,805
Selected Financial Ratios
Return on average assets		6.22%			4.14%			4.04%	4.01%
Return on average equity		31.11%			20.69%			20.20%	17.42%
Interest yield		14.97%			15.35%			14.99%	15.45%
Net interest margin		13.18%			13.25%			13.13%	13.43%
Reserve coverage		3.48%			2.25%			3.48%	2.25%
Delinquency status	[1]	0.52%			0.69%			0.52%	0.69%
Charge-off ratio		0.44%			2.05%			1.96%	2.30%
Operating Segments [Member] | Consumer Lending [Member] | Home Improvement [Member]
Segment Reporting Disclosure [Line Items]
Total interest income		$ 7,218			$ 5,184			$ 19,431	$ 14,187
Total interest expense		1,655			1,309			4,178	3,252
Net interest income		5,563			3,875			15,253	10,935
Provision for loan losses		745			(629)			3,041	733
Net interest income after provision for loan losses		4,818			4,504			12,212	10,202
Other income (expense), net		(2,700)			(2,000)			(7,002)	(5,356)
Income (loss) before income taxes		2,118			2,504			5,210	4,846
Income tax (provision) benefit		(541)			(648)			(1,332)	(1,255)
Net income (loss)		1,577			1,856			3,878	3,591
Balance Sheet Data
Total loans, net		310,691			228,491			310,691	228,491	244,716
Total assets		321,084			239,991			321,084	239,991	252,704
Total funds borrowed		$ 255,778			$ 190,871			$ 255,778	$ 190,871	201,605
Selected Financial Ratios
Return on average assets		2.06%			3.22%			1.84%	2.50%
Return on average equity		10.29%			16.09%			9.19%	11.34%
Interest yield		9.73%			9.46%			9.62%	9.44%
Net interest margin		7.50%			7.07%			7.53%	7.27%
Reserve coverage		1.51%			0.97%			1.51%	0.97%
Delinquency status	[1]	0.03%			0.11%			0.03%	0.11%
Charge-off ratio		0.09%			0.09%			0.44%	0.20%
Operating Segments [Member] | Commercial Lending [Member]
Segment Reporting Disclosure [Line Items]
Total interest income		$ 1,791			$ 1,842			$ 5,275	$ 5,359
Total interest expense		663			741			1,937	2,108
Net interest income		1,128			1,101			3,338	3,251
Provision for loan losses					364				364
Net interest income after provision for loan losses		1,128			737			3,338	2,887
Other income (expense), net		(712)			563			(2,191)	(532)
Income (loss) before income taxes		416			1,300			1,147	2,355
Income tax (provision) benefit		(104)			(314)			(286)	(568)
Net income (loss)		312			986			861	1,787
Balance Sheet Data
Total loans, net		68,042			64,646			68,042	64,646	66,405
Total assets		80,247			87,486			80,247	87,486	84,924
Total funds borrowed		$ 65,906			$ 69,658			$ 65,906	$ 69,658	68,666
Selected Financial Ratios
Return on average assets		1.49%			4.49%			1.37%	2.69%
Return on average equity		6.82%			22.45%			6.56%	13.43%
Interest yield		10.51%			11.09%			10.58%	11.59%
Net interest margin		6.62%			6.63%			6.69%	7.03%
Reserve coverage	[2]	0.00%			0.00%			0.00%	0.00%
Delinquency status	[1],[2]	2.67%			0.40%			2.67%	0.40%
Charge-off ratio	[3]	(0.02%)			4.93%			(0.01%)	1.77%
Operating Segments [Member] | Medallion Lending [Member]
Segment Reporting Disclosure [Line Items]
Total interest income		$ (909)			$ 975			$ 86	$ 2,482
Total interest expense		(56)			1,935			2,781	5,435
Net interest income		(853)			(960)			(2,695)	(2,953)
Provision for loan losses		37,196			1,858			49,489	15,374
Net interest income after provision for loan losses		(38,049)			(2,818)			(52,184)	(18,327)
Other income (expense), net		(9,738)			(2,762)			(20,603)	(8,106)
Income (loss) before income taxes		(47,787)			(5,580)			(72,787)	(26,433)
Income tax (provision) benefit		11,908			1,345			18,138	6,375
Net income (loss)		(35,879)			(4,235)			(54,649)	(20,058)
Balance Sheet Data
Total loans, net		33,521			112,003			33,521	112,003	105,022
Total assets		142,450			226,868			142,450	226,868	217,483
Total funds borrowed		$ 113,009			$ 180,040			$ 113,009	$ 180,040	176,825
Selected Financial Ratios
Return on average assets		(85.70%)			(7.26%)			(38.80%)	(10.82%)
Return on average equity					(36.30%)			(192.88%)	(54.12%)
Interest yield		(5.34%)			3.30%			0.13%	2.50%
Net interest margin		(3.89%)			(3.25%)			(4.12%)	(2.97%)
Reserve coverage		63.28%			18.22%			63.28%	18.22%
Delinquency status	[1]	8.31%			2.41%			8.31%	2.41%
Charge-off ratio		89.89%			5.20%			26.21%	18.29%
Intersegment Eliminations [Member]
Segment Reporting Disclosure [Line Items]
Total interest income		$ 378			$ 492			$ 1,253	$ 1,674
Total interest expense		2,604			1,615			6,933	5,313
Net interest income		(2,226)			(1,123)			(5,680)	(3,639)
Provision for loan losses		(4)						(4)	455
Net interest income after provision for loan losses		(2,222)			(1,123)			(5,676)	(4,094)
Other income (expense), net		(1,148)			(2,591)			(8,842)	(5,822)
Income (loss) before income taxes		(3,370)			(3,714)			(14,518)	(9,916)
Income tax (provision) benefit		2,261			2,780			4,426	4,930
Net income (loss)		(1,109)			(934)			(10,092)	(4,986)
Balance Sheet Data
Total loans, net		3,334			3,563			3,334	3,563	3,362
Total assets		231,923			229,734			231,923	229,734	247,641
Total funds borrowed		$ 199,312			$ 178,793			$ 199,312	$ 178,793	$ 150,898
Selected Financial Ratios
Return on average assets		(8.78%)			(1.54%)			(5.45%)	(2.90%)
Return on average equity		(54.58%)			(7.81%)			(22.64%)	(11.52%)

[1] Loans 90 days or more past due.

[2] Ratio is based on total commercial lending balances, and relates solely to the legacy commercial loan business.

[3] Ratio is based on total commercial lending balances, and relates to the total loan business.