Loans - Recorded Investment for Consumer Loans, Credit Quality based on Status of Loan and Payment Activity (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans after net deferred loan fees and costs	$ 1,091,131	$ 846,374	$ 831,015
Performing	335	116	119
Consumer - Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Performing	3,891	3,928
Consumer - Credit [Member] | Performing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Performing	3,858	3,909
Consumer - Credit [Member] | Nonperforming [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Performing	33	19
Consumer - Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Performing	45,209	38,127
Consumer - Other [Member] | Performing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Performing	45,144	38,073
Consumer - Other [Member] | Nonperforming [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Performing	65	54
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans after net deferred loan fees and costs	158,957	80,232	82,368
Performing	186	116	$ 119
Pass [Member] | Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans after net deferred loan fees and costs	156,743	79,121
5 [Member] | Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans after net deferred loan fees and costs	228	232
6 [Member] | Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans after net deferred loan fees and costs	$ 1,986	$ 879