Loans - Loans on Non-Accrual Status (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans	$ 2,682	$ 1,697
Troubled debt restructuring, non-accrual	1,395	1,404
Commercial Real Estate Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans	216	213
Commercial Real Estate Non-Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans	504	517
Commercial Loans [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans	78
Consumer Loans [Member] | Home Equity Term Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans	68
Consumer Loans [Member] | Home Equity Lines of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans	68	72
Consumer Loans [Member] | Residential Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans	$ 1,748	810
Consumer Loans [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total non-accrual loans		$ 85