Fair Value of Assets and Liabilities - Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis (Parenthetical) (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Allowance for impaired loans	$ 605	$ 630	$ 545
Fair Value, Measurements, Nonrecurring [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Allowance for impaired loans	$ 605	$ 630