Fair Value Measurements - Schedule of Quantitative Information of Assets Measured at Fair Value on Nonrecurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Level III [Member] | Discounted Cash Flow [Member] | Mortgage Servicing Rights [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	1.50%	1.50%
Level III [Member] | Discounted Cash Flow [Member] | Minimum [Member] | Impaired Loans [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Remaining term	5 months	3 months
Discount rate	3.10%	7.10%
Level III [Member] | Discounted Cash Flow [Member] | Minimum [Member] | Mortgage Servicing Rights [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Remaining term	15 months	12 months
Level III [Member] | Discounted Cash Flow [Member] | Maximum [Member] | Impaired Loans [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Remaining term	28 years	29 years
Discount rate	8.30%	12.00%
Level III [Member] | Discounted Cash Flow [Member] | Maximum [Member] | Mortgage Servicing Rights [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Remaining term	30 years	30 years
Level III [Member] | Discounted Cash Flow [Member] | Weighted Average [Member] | Impaired Loans [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Remaining term	67 months	62 months
Discount rate	4.60%	7.50%
Level III [Member] | Discounted Cash Flow [Member] | Weighted Average [Member] | Mortgage Servicing Rights [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Remaining term		244 months
Discount rate	1.50%	1.50%
Level III [Member] | Appraisal of Collateral [Member] | Impaired Loans [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Liquidation expense	(10.00%)	(10.00%)
Level III [Member] | Appraisal of Collateral [Member] | Minimum [Member] | Impaired Loans [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Appraisal adjustments	(20.00%)	(20.00%)
Level III [Member] | Appraisal of Collateral [Member] | Maximum [Member] | Impaired Loans [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Appraisal adjustments	(25.00%)	(25.00%)
Level III [Member] | Appraisal of Collateral [Member] | Weighted Average [Member] | Impaired Loans [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Appraisal adjustments	(24.00%)	(24.00%)
Liquidation expense	(10.00%)	(10.00%)
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Estimate	$ 8,551	$ 9,856
Fair Value, Measurements, Nonrecurring [Member] | Mortgage Servicing Rights [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Estimate	224	225
Fair Value, Measurements, Nonrecurring [Member] | Level III [Member] | Impaired Loans [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Estimate	8,551	9,856
Fair Value, Measurements, Nonrecurring [Member] | Level III [Member] | Mortgage Servicing Rights [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Estimate	224	225
Fair Value, Measurements, Nonrecurring [Member] | Level III [Member] | Discounted Cash Flow [Member] | Impaired Loans [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Estimate	6,315	8,663
Fair Value, Measurements, Nonrecurring [Member] | Level III [Member] | Discounted Cash Flow [Member] | Mortgage Servicing Rights [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Estimate	224	225
Fair Value, Measurements, Nonrecurring [Member] | Level III [Member] | Appraisal of Collateral [Member] | Impaired Loans [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Estimate	$ 2,236	$ 1,193