Loans - Recorded Investment for Consumer Loans, Credit Quality based on Status of Loan and Payment Activity (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans after net deferred loan fees and costs	$ 1,158,696	$ 846,374	$ 838,698
Performing	47	116	118
Consumer - Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Performing	3,867	3,928
Consumer - Credit [Member] \| Performing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Performing	3,867	3,909
Consumer - Credit [Member] \| Nonperforming [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Performing		19
Consumer - Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Performing	45,851	38,127
Consumer - Other [Member] \| Performing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Performing	45,752	38,073
Consumer - Other [Member] \| Nonperforming [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Performing	99	54
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans after net deferred loan fees and costs	158,458	80,232	82,629
Performing	47	116	$ 118
Pass [Member] \| Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans after net deferred loan fees and costs	155,346	79,121
5 [Member] \| Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans after net deferred loan fees and costs	227	232
6 [Member] \| Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans after net deferred loan fees and costs	$ 2,885	$ 879