Loans Receivable and Allowance for Loan Losses - Average Recorded Investment in Impaired Loans and Related Interest Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014 Contract	Sep. 30, 2013	Sep. 30, 2014 Contract	Sep. 30, 2013	Dec. 31, 2013 Contract
Financing Receivable, Impaired [Line Items]
Financing Receivable Modified Balance End Of Period Number Of Contract	25		25		12
Financing Receivable Modified Balance End Of Period	$ 4,153		$ 4,153		$ 7,535
Average Impaired Balance	20,497	20,923	21,718	20,044
Interest Income Recognized	72	187	216	365
Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Impaired [Line Items]
Average Impaired Balance	3,681	4,249	3,965	3,270
Interest Income Recognized	1	41	9	99
Commercial Real Estate [Member] | Non-Owner Occupied [Member]
Financing Receivable, Impaired [Line Items]
Average Impaired Balance	7,361	3,980	7,205	3,605
Interest Income Recognized	46	50	137	86
Commercial Real Estate [Member] | Multi - Family [Member]
Financing Receivable, Impaired [Line Items]
Average Impaired Balance	98	168	234	89
Interest Income Recognized	0	16	0	16
Commercial Real Estate [Member] | Non-Owner Occupied Residential [Member]
Financing Receivable, Impaired [Line Items]
Average Impaired Balance	1,905	5,108	2,603	4,875
Interest Income Recognized	0	45	2	60
Acquisition and Development [Member] | 1-4 Family Residential Construction [Member]
Financing Receivable, Impaired [Line Items]
Average Impaired Balance	0	345	0	602
Interest Income Recognized	0	0	0	0
Acquisition and Development [Member] | Commercial and Land Development [Member]
Financing Receivable, Impaired [Line Items]
Average Impaired Balance	1,286	2,613	1,787	2,967
Interest Income Recognized	9	0	20	2
Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
Average Impaired Balance	1,263	1,875	1,676	1,724
Interest Income Recognized	0	0	2	65
Residential Mortgage [Member] | First Lien [Member]
Financing Receivable, Impaired [Line Items]
Average Impaired Balance	4,772	2,421	4,068	2,528
Interest Income Recognized	15	29	45	31
Residential Mortgage [Member] | Home Equity - Term [Member]
Financing Receivable, Impaired [Line Items]
Average Impaired Balance	72	47	90	47
Interest Income Recognized	0	2	0	2
Residential Mortgage [Member] | Home Equity - Lines of Credit [Member]
Financing Receivable, Impaired [Line Items]
Average Impaired Balance	49	116	85	336
Interest Income Recognized	0	4	0	4
Installment and Other Loans [Member]
Financing Receivable, Impaired [Line Items]
Average Impaired Balance	10	1	5	1
Interest Income Recognized	1	0	1	0
Nonaccruing [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable Modified Balance End Of Period Number Of Contract	15		15		6
Financing Receivable Modified Balance End Of Period	2,418		2,418		1,547
Nonaccruing [Member] | Commercial Real Estate [Member] | Owner-Occupied [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable Modified Balance End Of Period Number Of Contract	1		1		1
Financing Receivable Modified Balance End Of Period	49		49		71
Nonaccruing [Member] | Commercial Real Estate [Member] | Non-Owner Occupied [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable Modified Balance End Of Period Number Of Contract	1		1		1
Financing Receivable Modified Balance End Of Period	686		686		694
Nonaccruing [Member] | Commercial Real Estate [Member] | Non-Owner Occupied Residential [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable Modified Balance End Of Period Number Of Contract	0		0		1
Financing Receivable Modified Balance End Of Period	0		0		193
Nonaccruing [Member] | Commercial and Industrial [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable Modified Balance End Of Period Number Of Contract	0		0		2
Financing Receivable Modified Balance End Of Period	0		0		310
Nonaccruing [Member] | Residential Mortgage [Member] | First Lien [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable Modified Balance End Of Period Number Of Contract	12		12		1
Financing Receivable Modified Balance End Of Period	1,669		1,669		279
Nonaccruing [Member] | Residential Mortgage [Member] | Consumer [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable Modified Balance End Of Period Number Of Contract	1		1		0
Financing Receivable Modified Balance End Of Period	$ 14		$ 14		$ 0