Loans and Allowance for Loan Losses - Non-Accrual Loans, Loan Still Accruing and Past Due 90 Days or More Restructured Loans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Non Accrual Loans Segregated By Class Of Loans [Line Items]
Non-accrual loans	$ 21,800		$ 19,975
Loans still accruing and past due 90 days or more	97		96
Restructured loans	0	[1]	0	[1]
Total	$ 21,897		$ 20,071

[1] * Restructured loans whose interest collection, after considering economic and business conditions and collection efforts, are doubtful are included in non-accrual loans.