Fair Value Measurement - Assets and Liabilities Measured on Non-recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Mortgage Servicing Rights [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Mortgage servicing rights	$ 2,704	$ 604
Fair Value, Measurements, Nonrecurring [Member] | Nonresidential [Member] | Commercial Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans	6,458	2,857
Other real estate owned, net	175	175
Fair Value, Measurements, Nonrecurring [Member] | Secured [Member] | Commercial Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans	546
Fair Value, Measurements, Nonrecurring [Member] | Home Equity [Member] | Consumer Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans	3	392
Fair Value, Measurements, Nonrecurring [Member] | Auto [Member] | Consumer Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans	4	1
Fair Value, Measurements, Nonrecurring [Member] | Marine [Member] | Consumer Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans	163
Fair Value, Measurements, Nonrecurring [Member] | Recreational Vehicle [Member] | Consumer Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans	213
Fair Value, Measurements, Nonrecurring [Member] | Construction [Member] | Commercial Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other real estate owned, net	785	785
Fair Value, Measurements, Nonrecurring [Member] | Land [Member] | Commercial Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans		175
Significant Other Observable Inputs (Level 2) [Member] | Mortgage Servicing Rights [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Mortgage servicing rights	2,704	604
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member] | Nonresidential [Member] | Commercial Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans	6,458	2,857
Other real estate owned, net	175	175
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member] | Secured [Member] | Commercial Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans	546
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member] | Home Equity [Member] | Consumer Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans	3	392
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member] | Auto [Member] | Consumer Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans	4	1
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member] | Marine [Member] | Consumer Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans	163
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member] | Recreational Vehicle [Member] | Consumer Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans	213
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member] | Construction [Member] | Commercial Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other real estate owned, net	785	785
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member] | Land [Member] | Commercial Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans		175
Residential Mortgage Loans [Member] | Fair Value, Measurements, Nonrecurring [Member] | One-to Four-Family [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans	867	1,493
Other real estate owned, net	344	1,088
Residential Mortgage Loans [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member] | One-to Four-Family [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired loans	867	1,493
Other real estate owned, net	$ 344	$ 1,088