Disclosures about Fair Value of Assets and Liabilities - Other Assets Measured at Fair Value on Nonrecurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Significant Unobservable Inputs (Level 3) [Member] | Impaired Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans	$ 6,803	$ 9,464
Significant Unobservable Inputs (Level 3) [Member] | Mortgage Servicing Rights [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans	8,874	7,642
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans	6,803	9,464
Fair Value, Measurements, Nonrecurring [Member] | Mortgage Servicing Rights [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans	8,874	7,642
Fair Value, Measurements, Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Impaired Loans [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans	6,803	9,464
Fair Value, Measurements, Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Mortgage Servicing Rights [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans	$ 8,874	$ 7,642