Allowance for Loan Losses - Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
With No Related Allowance [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	$ 1,751		$ 1,751		$ 2,145
Unpaid Principal Balance	2,523		2,523		2,535
Related Allowance	0		0		0
Average Recorded Investment	1,838	2,198	1,800	1,824
Interest Income Recognized	8	1	7	16
With No Related Allowance [Member] | Construction [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	12		12		14
Unpaid Principal Balance	12		12		14
Related Allowance	0		0		0
Average Recorded Investment	0	0	0	0
Interest Income Recognized	0	0	0	0
With No Related Allowance [Member] | Land, Farmland, Ag Loans [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	458		458		558
Unpaid Principal Balance	872		872		972
Related Allowance	0		0		0
Average Recorded Investment	458	1,024	508	667
Interest Income Recognized	3	1	7	16
With No Related Allowance [Member] | Residential [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	150		150		0
Unpaid Principal Balance	197		197		0
Related Allowance	0		0		0
Average Recorded Investment	153	567	154	551
Interest Income Recognized	0	0	0	0
With No Related Allowance [Member] | Commercial [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	1,066		1,066		1,572
Unpaid Principal Balance	1,377		1,377		1,619
Related Allowance	0		0		0
With No Related Allowance [Member] | Commercial and Industrial [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	65		65		0
Unpaid Principal Balance	65		65		0
Related Allowance	0		0		0
Average Recorded Investment	65	103	65	102
Interest Income Recognized	0	0	0	0
With No Related Allowance [Member] | Multi Family [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	0		0		1
Unpaid Principal Balance	0		0		661
Related Allowance	0		0		0
Average Recorded Investment	0	0	0	0
Interest Income Recognized	0	0	0	0
With No Related Allowance [Member] | Consumer [Member]
Impaired Financing Receivable [Abstract]
Average Recorded Investment	0	0	0	0
Interest Income Recognized	0	0	0	0
With No Related Allowance [Member] | Commercial & Non-Residential [Member]
Impaired Financing Receivable [Abstract]
Average Recorded Investment	1,162	504	1,073	504
Interest Income Recognized	5	0	0	0
With Related Allowance [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	20,896		20,896		20,582
Unpaid Principal Balance	21,130		21,130		21,001
Related Allowance	1,455		1,455		1,418
Average Recorded Investment	21,063	25,534	21,133	25,646
Interest Income Recognized	224	284	450	583
With Related Allowance [Member] | Construction [Member]
Impaired Financing Receivable [Abstract]
Average Recorded Investment	13	19	13	18
Interest Income Recognized	0	0	0	0
With Related Allowance [Member] | Land, Farmland, Ag Loans [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	222		222		230
Unpaid Principal Balance	222		222		230
Related Allowance	13		13		68
Average Recorded Investment	223	246	226	243
Interest Income Recognized	3	2	7	9
With Related Allowance [Member] | Residential [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	11,530		11,530		11,107
Unpaid Principal Balance	11,717		11,717		11,473
Related Allowance	675		675		500
Average Recorded Investment	11,605	11,856	11,617	11,756
Interest Income Recognized	107	94	219	194
With Related Allowance [Member] | Commercial [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	2,580		2,580		3,674
Unpaid Principal Balance	2,580		2,580		3,700
Related Allowance	229		229		369
With Related Allowance [Member] | Commercial and Industrial [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	90		90		539
Unpaid Principal Balance	90		90		539
Related Allowance	10		10		25
Average Recorded Investment	94	389	98	377
Interest Income Recognized	2	5	3	12
With Related Allowance [Member] | Multi Family [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	6,072		6,072		4,541
Unpaid Principal Balance	6,072		6,072		4,541
Related Allowance	450		450		416
Average Recorded Investment	6,083	4,622	6,096	4,611
Interest Income Recognized	75	54	146	107
With Related Allowance [Member] | Consumer [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	402		402		491
Unpaid Principal Balance	449		449		518
Related Allowance	78		78		40
Average Recorded Investment	452	298	478	280
Interest Income Recognized	1	2	3	8
With Related Allowance [Member] | Commercial & Non-Residential [Member]
Impaired Financing Receivable [Abstract]
Average Recorded Investment	2,593	8,104	2,605	8,361
Interest Income Recognized	$ 36	$ 127	$ 72	$ 253