Loans and Allowance for Loan Losses - Summary of Activity in Allowance for Loan Losses (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - beginning balance		$ 54,057	$ 36,862	$ 46,093	$ 36,395
Total charge-offs		(8,027)	(14,176)	(19,205)	(30,038)
Total recoveries		4,006	2,813	6,607	5,799
Net charge-offs	[1]	(4,021)	(11,363)	(12,598)	(24,239)
Provision for loan losses		16,941	15,171	33,482	28,514
Allowance for loan losses - ending balance	[2],[3]	66,977	40,670	66,977	40,670
Recreation [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - beginning balance				18,075
Total charge-offs		(5,708)	(4,395)	(13,951)	(10,921)
Total recoveries		2,143	1,962	4,005	3,558
Allowance for loan losses - ending balance		27,021		27,021
Home Improvement [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - beginning balance				2,608
Total charge-offs		(548)	(539)	(1,558)	(1,088)
Total recoveries		352	453	726	843
Allowance for loan losses - ending balance		4,072		4,072
Medallion [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses - beginning balance				25,410
Total charge-offs		(1,771)	(9,242)	(3,696)	(18,029)
Total recoveries		1,511	$ 398	1,876	$ 1,398
Allowance for loan losses - ending balance		$ 35,884		$ 35,884

[1] As of June 30, 2020, cumulative net charge-offs of loans and loan collateral in process of foreclosure in the medallion loan portfolio were $245,058, representing collection opportunities for the Company.

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

[3] Includes $2,025 of a general reserve for the Company, for current and performing medallion loans under 90 days past due, as an additional buffer against future losses, representing 3% of the total allowance, and 1.94% of the medallion loans under 90 days past due as of June 30, 2020. This figure excludes $17,351 of a general reserve on loans at the Bank, which was netted against loan balances at consolidation on April 2, 2018. Subsequent to April 2, 2018, the Bank recorded a general reserve benefit of $11,555.