Loans and Allowance for Loan Losses - Summary of Activity in Allowance for Loan Losses (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - beginning balance		$ 66,977	$ 40,670	$ 46,093	$ 36,395
Total charge-offs		(19,686)	(9,209)	(38,894)	(39,248)
Total recoveries		3,470	3,315	10,080	9,115
Net charge-offs	[1]	(16,216)	(5,894)	(28,814)	(30,133)
Provision for loan losses		39,749	8,337	73,231	36,851
Allowance for loan losses - ending balance	[2],[3]	90,510	43,113	90,510	43,113
Recreation [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - beginning balance				18,075
Total charge-offs		(3,595)	(5,444)	(17,546)	(16,366)
Total recoveries		2,745	1,955	6,750	5,513
Allowance for loan losses - ending balance		27,982		27,982
Home Improvement [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - beginning balance				2,608
Total charge-offs		(643)	(568)	(2,202)	(1,655)
Total recoveries		578	517	1,304	1,360
Allowance for loan losses - ending balance		4,751		4,751
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total charge-offs			(819)		(819)
Total recoveries		3		3
Medallion [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - beginning balance				25,410
Total charge-offs		(15,448)	(2,378)	(19,146)	(20,408)
Total recoveries		144	$ 843	2,023	$ 2,242
Allowance for loan losses - ending balance		$ 57,777		$ 57,777

[1] As of September 30, 2020, cumulative net charge-offs of loans and loan collateral in process of foreclosure in the medallion loan portfolio were $268,745, representing collection opportunities for the Company.

[2] As of September 30, 2020, the general reserves previously recorded for the Company’s medallion loan portfolio had been reversed as all loans had been deemed impaired and written down to collateral value.    

[3] As of September 30, 2020, there was no allowance for loan losses and net charge-offs related to the strategic partnership loans.