Fair Value Measurement - Quantitative Information About Level 3 Fair Value Measurements for Financial Instruments Measured at Fair Value on Nonrecurring Basis (Detail) - Fair Value, Measurements, Nonrecurring [Member] - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Impaired Loans [Member] | Nonresidential [Member] | Commercial Loans [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Fair Value	$ 6,038	$ 2,857
Impaired Loans [Member] | Nonresidential [Member] | Commercial Loans [Member] | Minimum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	0.00%	9.19%
Impaired Loans [Member] | Nonresidential [Member] | Commercial Loans [Member] | Maximum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	35.00%	12.38%
Impaired Loans [Member] | Nonresidential [Member] | Commercial Loans [Member] | Weighted Average [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	15.00%	10.79%
Impaired Loans [Member] | Secured [Member] | Commercial Loans [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Fair Value	$ 148
Impaired Loans [Member] | Secured [Member] | Commercial Loans [Member] | Minimum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	0.00%
Impaired Loans [Member] | Secured [Member] | Commercial Loans [Member] | Maximum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	31.00%
Impaired Loans [Member] | Secured [Member] | Commercial Loans [Member] | Weighted Average [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	12.75%
Impaired Loans [Member] | Home Equity [Member] | Consumer Loans [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Fair Value	$ 208	$ 392
Impaired Loans [Member] | Home Equity [Member] | Consumer Loans [Member] | Minimum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	0.00%	0.00%
Impaired Loans [Member] | Home Equity [Member] | Consumer Loans [Member] | Maximum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	17.85%	17.85%
Impaired Loans [Member] | Home Equity [Member] | Consumer Loans [Member] | Weighted Average [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	8.93%	8.93%
Impaired Loans [Member] | Auto [Member] | Consumer Loans [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Fair Value	$ 2
Impaired Loans [Member] | Auto [Member] | Consumer Loans [Member] | Minimum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	0.00%
Impaired Loans [Member] | Auto [Member] | Consumer Loans [Member] | Maximum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	10.00%
Impaired Loans [Member] | Auto [Member] | Consumer Loans [Member] | Weighted Average [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	10.00%
Impaired Loans [Member] | Marine [Member] | Consumer Loans [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Fair Value	$ 163
Impaired Loans [Member] | Marine [Member] | Consumer Loans [Member] | Minimum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	0.00%
Impaired Loans [Member] | Marine [Member] | Consumer Loans [Member] | Maximum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	37.00%
Impaired Loans [Member] | Marine [Member] | Consumer Loans [Member] | Weighted Average [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	37.00%
Impaired Loans [Member] | Recreational Vehicle [Member] | Consumer Loans [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Fair Value	$ 200
Impaired Loans [Member] | Recreational Vehicle [Member] | Consumer Loans [Member] | Minimum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	0.00%
Impaired Loans [Member] | Recreational Vehicle [Member] | Consumer Loans [Member] | Maximum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	37.00%
Impaired Loans [Member] | Recreational Vehicle [Member] | Consumer Loans [Member] | Weighted Average [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	37.00%
Impaired Loans [Member] | Land [Member] | Commercial Loans [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Fair Value		$ 175
Impaired Loans [Member] | Land [Member] | Commercial Loans [Member] | Minimum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales		0.00%
Impaired Loans [Member] | Land [Member] | Commercial Loans [Member] | Maximum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales		27.47%
Impaired Loans [Member] | Land [Member] | Commercial Loans [Member] | Weighted Average [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales		13.74%
Impaired Loans [Member] | Residential Mortgage Loans [Member] | One-to Four-Family [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Fair Value	$ 847	$ 1,493
Impaired Loans [Member] | Residential Mortgage Loans [Member] | One-to Four-Family [Member] | Minimum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	0.00%	0.00%
Impaired Loans [Member] | Residential Mortgage Loans [Member] | One-to Four-Family [Member] | Maximum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	10.77%	10.77%
Impaired Loans [Member] | Residential Mortgage Loans [Member] | One-to Four-Family [Member] | Weighted Average [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	4.27%	4.27%
Other Real Estate Owned [Member] | Nonresidential [Member] | Commercial Loans [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Fair Value		$ 175
Other Real Estate Owned [Member] | Nonresidential [Member] | Commercial Loans [Member] | Minimum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales		40.00%
Other Real Estate Owned [Member] | Nonresidential [Member] | Commercial Loans [Member] | Maximum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales		60.00%
Other Real Estate Owned [Member] | Nonresidential [Member] | Commercial Loans [Member] | Weighted Average [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales		50.00%
Other Real Estate Owned [Member] | Construction [Member] | Commercial Loans [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Fair Value	$ 748	$ 785
Other Real Estate Owned [Member] | Construction [Member] | Commercial Loans [Member] | Minimum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	0.00%	0.00%
Other Real Estate Owned [Member] | Construction [Member] | Commercial Loans [Member] | Maximum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	25.00%	50.00%
Other Real Estate Owned [Member] | Construction [Member] | Commercial Loans [Member] | Weighted Average [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	10.875%	21.71%
Other Real Estate Owned [Member] | Residential Mortgage Loans [Member] | One-to Four-Family [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Fair Value	$ 290	$ 1,088
Other Real Estate Owned [Member] | Residential Mortgage Loans [Member] | One-to Four-Family [Member] | Minimum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	0.00%	0.00%
Other Real Estate Owned [Member] | Residential Mortgage Loans [Member] | One-to Four-Family [Member] | Maximum [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	37.10%	40.50%
Other Real Estate Owned [Member] | Residential Mortgage Loans [Member] | One-to Four-Family [Member] | Weighted Average [Member] | Sales Comparison Approach [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Adjustment for differences between comparable sales	29.05%	15.51%