Loans and Allowance for Loan Losses - Summary of Aging of Loans (Detail) - USD ($) $ in Thousands		Sep. 30, 2018		Apr. 02, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		$ 50,695			$ 88,886
Current		1,013,648			230,341
Total		1,064,343	[1]		319,227
Accruing					265
Recreation [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		22,233
Current		534,065
Total	[1]	556,298
Home Improvement [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		1,169
Current		170,825
Total	[1]	171,994
Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		987			749
Current		81,571			90,062
Total		82,558	[1]		90,811
Medallion [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		26,306			88,137
Current		227,187			140,279
Total		253,493	[1]		228,416
Accruing					265
Secured Mezzanine Term Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current					88,334
Total					88,334
Other Secured Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60					749
Current					1,728
Total					2,477
31-60 [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		27,239			16,049
31-60 [Member] | Recreation [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		14,974
31-60 [Member] | Home Improvement [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		782
31-60 [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		471
31-60 [Member] | Medallion [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		11,012			16,049
61-90 [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		9,395		$ 12,387	12,387
61-90 [Member] | Recreation [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		4,095
61-90 [Member] | Home Improvement [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		212
61-90 [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		95
61-90 [Member] | Medallion [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		4,993			12,387
91+ [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		14,061			60,450
91+ [Member] | Recreation [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		3,164
91+ [Member] | Home Improvement [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		175
91+ [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		421			749
91+ [Member] | Medallion [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60		$ 10,301			59,701
91+ [Member] | Other Secured Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60					$ 749

[1] Excludes loan premiums of $10,606 resulting from purchase price accounting and $14,596 of capitalized loan origination costs.