Loans and Allowance for Loan Losses - Summary of Performance Status of Loan (Detail) $ in Thousands	Sep. 30, 2018 USD ($)
Financing Receivable, Recorded Investment [Line Items]
Status of loans	$ 1,089,545
Recreation [Member]
Financing Receivable, Recorded Investment [Line Items]
Status of loans	575,875
Home Improvement [Member]
Financing Receivable, Recorded Investment [Line Items]
Status of loans	169,642
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Status of loans	82,558
Medallion [Member]
Financing Receivable, Recorded Investment [Line Items]
Status of loans	261,470
Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Status of loans	1,040,843
Performing [Member] | Recreation [Member]
Financing Receivable, Recorded Investment [Line Items]
Status of loans	570,800
Performing [Member] | Home Improvement [Member]
Financing Receivable, Recorded Investment [Line Items]
Status of loans	169,475
Performing [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Status of loans	77,155
Performing [Member] | Medallion [Member]
Financing Receivable, Recorded Investment [Line Items]
Status of loans	223,413
Non - Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Status of loans	48,702
Non - Performing [Member] | Recreation [Member]
Financing Receivable, Recorded Investment [Line Items]
Status of loans	5,075
Non - Performing [Member] | Home Improvement [Member]
Financing Receivable, Recorded Investment [Line Items]
Status of loans	167
Non - Performing [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Status of loans	5,403
Non - Performing [Member] | Medallion [Member]
Financing Receivable, Recorded Investment [Line Items]
Status of loans	$ 38,057