Commitments and Off-Balance Sheet Risk - Maximum Exposure to Credit Losses for Loan Commitments and Standby Letters of Credit Outstanding (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual amounts of financial instruments with off-balance sheet risk	$ 374,543,000	$ 334,768,000
Commercial unused lines of credit [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual amounts of financial instruments with off-balance sheet risk	257,937,000	222,237,000
Unused lines of credit secured by 1 - 4 family residential properties [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual amounts of financial instruments with off-balance sheet risk	23,429,000	24,250,000
Credit card unused lines of credit [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual amounts of financial instruments with off-balance sheet risk	9,013,000	8,512,000
Other consumer unused lines of credit [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual amounts of financial instruments with off-balance sheet risk	5,695,000	4,613,000
Commitments to make loans [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual amounts of financial instruments with off-balance sheet risk	58,799,000	64,565,000
Standby letters of credit [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual amounts of financial instruments with off-balance sheet risk	$ 19,670,000	$ 10,591,000