Loans, net and allowance for loan losses - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 Loans SecurityLoan	Dec. 31, 2012 SecurityLoan Loans	Dec. 31, 2011
Receivables [Abstract]
Net deferred loan costs	$ 24
Loans outstanding to directors, executive officers, principal stockholders or to their affiliates	15,513	14,205
Advances and repayments of loans receivable	12,429	13,737
Interest income recognized using the cash-basis method on impaired loans	0	0	0
Number of distressed loans	29	29
Credit adjustment on distressed loans	7,787	7,826
Total impaired loans	14,274	5,271	3,534
Impaired loans acquired	7,391
Loans receivable, related parties, considered as nonaccrual, past due or restructured or potential credit risk	2,487	351	368
Number of loans modified as troubled debt restructurings	0	0
Amount of defaults on loans considered troubled debt restructurings	0	0
Amount charge-offs as a result of the troubled debt restructurings	$ 0