Loans - Allowance for Loan Losses Disaggregated on the Basis of Impairment Methodology (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans individually evaluated for impairment	$ 14,971		$ 20,596	$ 19,423
Loans collectively evaluated for impairment	83,341		71,842	73,724
Ending balance	98,312	98,286	92,438	93,147	93,400	104,453
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans individually evaluated for impairment	13,104		16,682	15,912
Loans collectively evaluated for impairment	45,532		36,108	38,666
Ending balance	58,636	55,672	52,790	54,578	50,814	54,164
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans individually evaluated for impairment	1,867		3,914	3,511
Loans collectively evaluated for impairment	24,913		18,676	18,205
Ending balance	26,780	22,046	22,590	21,716	23,573	29,346
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans individually evaluated for impairment	0		0	0
Loans collectively evaluated for impairment	5,107		5,230	5,098
Ending balance	5,107	4,659	5,230	5,098	4,917	5,252
Consumer and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans individually evaluated for impairment	0		0	0
Loans collectively evaluated for impairment	7,789		5,010	4,682
Ending balance	7,789	6,427	5,010	4,682	4,130	3,507
Unallocated [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans individually evaluated for impairment	0		0	0
Loans collectively evaluated for impairment	0		6,818	7,073
Ending balance	$ 0	$ 9,482	$ 6,818	$ 7,073	$ 9,966	$ 12,184