Loans and Allowance for Loan and Lease Losses - Loans Accounted for on Non Accrual Basis (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	$ 4,570	$ 4,376
Commercial Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	812	812
Residential Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	2,427	2,212
Construction Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	836	836
Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	$ 495	$ 516