Loans and Allowance for Loan Losses - Components of Changes in Gross Loans (Detail) - USD ($) $ in Thousands		9 Months Ended		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2019		Dec. 31, 2018
Schedule Of Gross Real Estate And Loan Activity [Line Items]
Gross loans, beginning balance	[1]			$ 993,788
Charge-offs, net	[2]	$ (22,613)		(37,688)
Transfer to loans in process of foreclosure, net		(34,658)		(31,348)
Amortization of origination costs				(4,952)		$ (3,132)	[3]
Paid-in-kind interest				834		1,869	[3]
Gross loans, ending balance		993,788	[1]	1,136,694	[4]	993,788	[1]
Recreation [Member]
Schedule Of Gross Real Estate And Loan Activity [Line Items]
Gross loans, beginning balance	[1]			567,209
Transfer to loans in process of foreclosure, net		(9,289)		(14,512)
Gross loans, ending balance		567,209	[1]	689,810	[4]	567,209	[1]
Home Improvement [Member]
Schedule Of Gross Real Estate And Loan Activity [Line Items]
Gross loans, beginning balance	[1]			185,661
Gross loans, ending balance		185,661	[1]	250,830	[4]	185,661	[1]
Medallion [Member]
Schedule Of Gross Real Estate And Loan Activity [Line Items]
Gross loans, beginning balance	[1]			176,835
Transfer to loans in process of foreclosure, net		(25,369)		(16,836)
Gross loans, ending balance		176,835	[1]	126,287	[4]	176,835	[1]
Bank Holding Company Accounting [Member]
Schedule Of Gross Real Estate And Loan Activity [Line Items]
Gross loans, beginning balance				1,017,882
Loan originations				462,093
Principal payments				(251,653)
Charge-offs, net				(37,688)
Transfer to loans in process of foreclosure, net				(31,348)
Amortization of origination costs				(4,952)
Amortization of loan premium				(3,289)
FASB origination costs				8,976
Paid-in-kind interest				834
Gross loans, ending balance		1,017,882		1,160,855		1,017,882
Bank Holding Company Accounting [Member] | Recreation [Member]
Schedule Of Gross Real Estate And Loan Activity [Line Items]
Gross loans, beginning balance				587,038
Loan originations				301,403
Principal payments				(146,873)
Charge-offs, net				(17,419)
Transfer to loans in process of foreclosure, net				(14,512)
Amortization of origination costs				(6,428)
Amortization of loan premium				(247)
FASB origination costs				10,370
Gross loans, ending balance		587,038		713,332		587,038
Bank Holding Company Accounting [Member] | Home Improvement [Member]
Schedule Of Gross Real Estate And Loan Activity [Line Items]
Gross loans, beginning balance				183,155
Loan originations				142,112
Principal payments				(76,157)
Charge-offs, net				(786)
Amortization of origination costs				1,561
Amortization of loan premium				(416)
FASB origination costs				(2,145)
Gross loans, ending balance		183,155		247,324		183,155
Bank Holding Company Accounting [Member] | Commercial [Member]
Schedule Of Gross Real Estate And Loan Activity [Line Items]
Gross loans, beginning balance				64,083
Loan originations				18,578
Principal payments				(13,553)
Charge-offs, net				(819)
Amortization of origination costs				34
FASB origination costs				610
Paid-in-kind interest				834
Gross loans, ending balance		64,083		69,767		64,083
Bank Holding Company Accounting [Member] | Medallion [Member]
Schedule Of Gross Real Estate And Loan Activity [Line Items]
Gross loans, beginning balance				183,606
Principal payments				(15,070)
Charge-offs, net				(18,664)
Transfer to loans in process of foreclosure, net				(16,836)
Amortization of origination costs				(119)
Amortization of loan premium				(2,626)
FASB origination costs				141
Gross loans, ending balance		$ 183,606		$ 130,432		$ 183,606

[1] Excludes loan premiums of $9,047 resulting from purchase price accounting and $15,047 of capitalized loan origination costs.

[2] As of December 31, 2019, cumulative charge-offs of loans and loans in process of foreclosure in the medallion loan portfolio were $241,214, representing collection opportunities for the Company.

[3] Balance includes the nine months ended December 31, 2018 under Bank Holding Company Accounting and the three months ended March 31, 2018 under Investment Company Accounting.

[4] Excludes loan premiums of $5,758 resulting from purchase price accounting and $18,403 of capitalized loan origination costs.