Segment Reporting - Schedule of Segment Data (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Segment Reporting Disclosure [Line Items]
Total interest income	$ 32,644
Total Interest Expense	7,925
Net interest income	24,719
Provision for loan losses	30,576
Net interest income after loss provision	(5,857)
Sponsorship and race winning	5,228
Race team related expenses	(2,540)
Other income (expense)	(14,736)
Loss before income taxes/net investment loss before taxes	(17,905)
Income tax benefit (provision)	4,021	$ 7,018	$ 4,661	$ 8,990
Net Income (loss) after tax	(13,884)
Balance Sheet Data
Total loans net	1,128,698		1,128,698
Total assets	1,534,529		1,534,529		$ 1,077,357
Total funds borrowed	$ 1,226,342		$ 1,226,342
Selected Financial Ratios
Return on assets	(4.53%)
Return on equity	(22.00%)		(22.00%)
Interest yield	11.23%
Net interest margin	8.57%
Reserve coverage	1.86%
Delinquency ratio	1.32%
Charge off ratio	3.19%
RPAC Racing, LLC [Member]
Segment Reporting Disclosure [Line Items]
Total Interest Expense	$ 41
Net interest income	(41)
Net interest income after loss provision	(41)
Sponsorship and race winning	5,228
Race team related expenses	(2,540)
Other income (expense)	(2,237)
Loss before income taxes/net investment loss before taxes	410
Income tax benefit (provision)	(43)
Net Income (loss) after tax	367
Balance Sheet Data
Total assets	37,861		$ 37,861
Total funds borrowed	$ 7,578		$ 7,578
Selected Financial Ratios
Return on assets	3.89%
Return on equity	22.38%		22.38%
Operating Segments [Member] | Consumer Lending [Member] | Recreation [Member]
Segment Reporting Disclosure [Line Items]
Total interest income	$ 22,132
Total Interest Expense	2,136
Net interest income	19,996
Provision for loan losses	4,710
Net interest income after loss provision	15,286
Other income (expense)	(5,520)
Loss before income taxes/net investment loss before taxes	9,766
Income tax benefit (provision)	(2,162)
Net Income (loss) after tax	7,604
Balance Sheet Data
Total loans net	595,385		$ 595,385
Total assets	599,960		599,960
Total funds borrowed	$ 456,955		$ 456,955
Selected Financial Ratios
Return on assets	5.32%
Return on equity	23.33%		23.33%
Interest yield	15.62%
Net interest margin	14.12%
Reserve coverage	0.33%
Delinquency ratio	0.40%
Charge off ratio	0.82%
Operating Segments [Member] | Consumer Lending [Member] | Home Improvement [Member]
Segment Reporting Disclosure [Line Items]
Total interest income	$ 4,637
Total Interest Expense	739
Net interest income	3,898
Provision for loan losses	877
Net interest income after loss provision	3,021
Other income (expense)	(1,685)
Loss before income taxes/net investment loss before taxes	1,336
Income tax benefit (provision)	(296)
Net Income (loss) after tax	1,040
Balance Sheet Data
Total loans net	195,321		$ 195,321
Total assets	206,298		206,298
Total funds borrowed	$ 159,913		$ 159,913
Selected Financial Ratios
Return on assets	2.13%
Return on equity	9.74%		9.74%
Interest yield	10.02%
Net interest margin	8.43%
Reserve coverage	0.28%
Delinquency ratio	0.06%
Charge off ratio	0.30%
Operating Segments [Member] | Commercial Lending [Member]
Segment Reporting Disclosure [Line Items]
Total interest income	$ 2,322
Total Interest Expense	655
Net interest income	1,667
Provision for loan losses	175
Net interest income after loss provision	1,492
Other income (expense)	(1,110)
Loss before income taxes/net investment loss before taxes	382
Income tax benefit (provision)	(85)
Net Income (loss) after tax	297
Balance Sheet Data
Total loans net	79,930		$ 79,930
Total assets	109,261		109,261
Total funds borrowed	$ 68,224		$ 68,224
Selected Financial Ratios
Return on assets	1.05%
Return on equity	2.53%		2.53%
Interest yield	10.54%
Net interest margin	7.57%
Reserve coverage	0.22%
Delinquency ratio	0.27%
Charge off ratio	0.00%
Operating Segments [Member] | Medallion Lending [Member]
Segment Reporting Disclosure [Line Items]
Total interest income	$ 3,189
Total Interest Expense	3,373
Net interest income	(184)
Provision for loan losses	24,814
Net interest income after loss provision	(24,998)
Other income (expense)	(2,811)
Loss before income taxes/net investment loss before taxes	(27,809)
Income tax benefit (provision)	6,157
Net Income (loss) after tax	(21,652)
Balance Sheet Data
Total loans net	258,062		$ 258,062
Total assets	386,225		386,225
Total funds borrowed	$ 402,955		402,955
Selected Financial Ratios
Return on assets	(21.69%)
Interest yield	4.43%
Net interest margin	(0.26%)
Reserve coverage	6.77%
Delinquency ratio	4.49%
Charge off ratio	2.18%
Intersegment Eliminations [Member]
Segment Reporting Disclosure [Line Items]
Total interest income	$ 364
Total Interest Expense	981
Net interest income	(617)
Net interest income after loss provision	(617)
Other income (expense)	(1,373)
Loss before income taxes/net investment loss before taxes	(1,990)
Income tax benefit (provision)	450
Net Income (loss) after tax	(1,540)
Balance Sheet Data
Total assets	194,924		194,924
Total funds borrowed	$ 130,717		$ 130,717
Selected Financial Ratios
Return on assets	(2.99%)
Return on equity	(8.15%)		(8.15%)