Loans and Allowance for Loan Losses - Summary of Nonperforming Loan Portfolio (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment, With related allowance	$ 81,925	$ 26,878	$ 81,925	$ 26,878	$ 62,493
Unpaid principal balance, With related allowance	82,255	27,725	82,255	27,725	62,964
Related allowance, With related allowance	36,083	20,052	36,083	20,052	15,156
Average investment recorded, With related allowance	75,459	28,532	84,880	27,451
Interest income recognized, With related allowance	362	185	906	346
Recreation [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment, With related allowance	5,312	5,755	5,312	5,755	8,262
Unpaid principal balance, With related allowance	5,312	5,755	5,312	5,755	8,262
Related allowance, With related allowance	243	211	243	211	329
Average investment recorded, With related allowance	5,544	5,777	5,653	5,951
Interest income recognized, With related allowance	158	135	299	246
Home Improvement [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment, With related allowance	137	165	137	165	185
Unpaid principal balance, With related allowance	137	165	137	165	185
Related allowance, With related allowance	2	3	2	3	3
Average investment recorded, With related allowance	137	167	137	167
Interest income recognized, With related allowance	1		1
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment, With related allowance	15,246	8,743	15,246	8,743	11,862
Unpaid principal balance, With related allowance	15,251	8,838	15,251	8,838	11,867
Related allowance, With related allowance		455		455
Average investment recorded, With related allowance	15,360	6,656	15,359	5,776
Interest income recognized, With related allowance		30	1	73
Medallion [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded Investment, With related allowance	61,230	12,215	61,230	12,215	42,184
Unpaid principal balance, With related allowance	61,555	12,967	61,555	12,967	42,650
Related allowance, With related allowance	35,838	19,383	35,838	19,383	$ 14,824
Average investment recorded, With related allowance	54,418	15,932	63,731	15,557
Interest income recognized, With related allowance	$ 203	$ 20	$ 605	$ 27