Loans - Summary of Deferral Activity Related to Loan Modification Programs to Customers (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2020 USD ($) Loan	Dec. 31, 2019 USD ($)
Loan Modification Programs to Customer [Line Items]
Loans	$ 628,084	$ 551,633
Covid-19 [Member]
Loan Modification Programs to Customer [Line Items]
Loans	$ 629,608
Deferred # of Loans | Loan	204
Total COVID Loan Deferrals	$ 71,444
Percent of Portfolio Modified	11.00%
Remaining Balance in Deferment	$ 13,039
Remaining # of loans in Deferment | Loan	14
Covid-19 [Member] | RV [Member]
Loan Modification Programs to Customer [Line Items]
Loans	$ 9,118
Deferred # of Loans | Loan	14
Total COVID Loan Deferrals	$ 316
Percent of Portfolio Modified	3.00%
Remaining Balance in Deferment	$ 68
Remaining # of loans in Deferment | Loan	2
Covid-19 [Member] | Commercial [Member]
Loan Modification Programs to Customer [Line Items]
Loans	$ 211,647
Deferred # of Loans | Loan	64
Total COVID Loan Deferrals	$ 9,995
Percent of Portfolio Modified	5.00%
Remaining Balance in Deferment	$ 119
Remaining # of loans in Deferment | Loan	2
Covid-19 [Member] | Commercial Real Estate [Member]
Loan Modification Programs to Customer [Line Items]
Loans	$ 194,493
Deferred # of Loans | Loan	73
Total COVID Loan Deferrals	$ 56,789
Percent of Portfolio Modified	29.00%
Remaining Balance in Deferment	$ 12,341
Remaining # of loans in Deferment | Loan	3
Covid-19 [Member] | Construction [Member]
Loan Modification Programs to Customer [Line Items]
Loans	$ 28,875
Deferred # of Loans | Loan	3
Total COVID Loan Deferrals	$ 462
Percent of Portfolio Modified	2.00%
Covid-19 [Member] | Total Commercial [Member]
Loan Modification Programs to Customer [Line Items]
Loans	$ 435,015
Deferred # of Loans | Loan	140
Total COVID Loan Deferrals	$ 67,246
Percent of Portfolio Modified	15.00%
Remaining Balance in Deferment	$ 12,460
Remaining # of loans in Deferment | Loan	5
Covid-19 [Member] | Residential Real Estate [Member]
Loan Modification Programs to Customer [Line Items]
Loans	$ 176,256
Deferred # of Loans | Loan	34
Total COVID Loan Deferrals	$ 3,674
Percent of Portfolio Modified	2.00%
Remaining Balance in Deferment	$ 499
Remaining # of loans in Deferment | Loan	6
Covid-19 [Member] | Other Consumer [Member]
Loan Modification Programs to Customer [Line Items]
Loans	$ 9,219
Deferred # of Loans | Loan	16
Total COVID Loan Deferrals	$ 208
Percent of Portfolio Modified	2.00%
Remaining Balance in Deferment	$ 12
Remaining # of loans in Deferment | Loan	1
Covid-19 [Member] | Total Consumer [Member]
Loan Modification Programs to Customer [Line Items]
Loans	$ 194,593
Deferred # of Loans | Loan	64
Total COVID Loan Deferrals	$ 4,198
Percent of Portfolio Modified	2.00%
Remaining Balance in Deferment	$ 579
Remaining # of loans in Deferment | Loan	9