Financial Instruments (Schedule of Assets Recorded at Fair Value on Nonrecurring Basis) (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, nonrecurring basis	$ 536	$ 1,575
Impaired Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, nonrecurring basis	466	1,167
Foreclosed assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, nonrecurring basis	70	408
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, nonrecurring basis	536	1,575
Significant Unobservable Inputs (Level 3) | Impaired Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, nonrecurring basis	466	1,167
Significant Unobservable Inputs (Level 3) | Foreclosed assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, nonrecurring basis	$ 70	$ 408