Off-Balance Sheet Commitments - Distribution of Undisbursed Loan Commitments (Detail)

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Off-Balance Sheet Commitments - Distribution of Undisbursed Loan Commitments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Loss Contingencies [Line Items]
Total Undisbursed Loan Commitments	$ 212,885	$ 196,725
Commitments to Extend Credit [Member]
Loss Contingencies [Line Items]
Total Undisbursed Loan Commitments	182,746	158,748
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Total Undisbursed Loan Commitments	10,588	12,742
Commercial Letters of Credit [Member]
Loss Contingencies [Line Items]
Total Undisbursed Loan Commitments	6,092	9,298
Unused Credit Card Lines [Member]
Loss Contingencies [Line Items]
Total Undisbursed Loan Commitments	$ 13,459	$ 15,937