Allowance for Loan Losses - Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
With No Related Allowance [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	$ 663		$ 663		$ 2,145
Unpaid Principal Balance	1,970		1,970		3,266
Related Allowance	0		0		0
Average Recorded Investment	809	1,855	751	1,157
Interest Income Recognized	0	37	11	0
With No Related Allowance [Member] | Construction [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	11		11		14
Unpaid Principal Balance	11		11		14
Related Allowance	0		0		0
Average Recorded Investment	11	0	11	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	0	483	0
Interest Income Recognized	7	0	10	0
With No Related Allowance [Member] | Residential [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	126		126		0
Unpaid Principal Balance	172		172		0
Related Allowance	0		0		0
Average Recorded Investment	138	619	129	551
Interest Income Recognized	0	1	1	0
With No Related Allowance [Member] | Commercial and Non-Residential [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	36		36		1,572
Unpaid Principal Balance	222		222		1,619
Related Allowance	0		0		0
Average Recorded Investment	153	1,170	95	504
Interest Income Recognized	0	36	0	0
With No Related Allowance [Member] | Commercial and Industrial [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	32		32		0
Unpaid Principal Balance	32		32		0
Related Allowance	0		0		0
Average Recorded Investment	49	66	33	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	661		661		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 Related Allowance [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	21,991		21,991		20,582
Unpaid Principal Balance	22,223		22,223		21,001
Related Allowance	1,715		1,715		1,418
Average Recorded Investment	22,168	22,854	22,191	25,646
Interest Income Recognized	224	497	714	583
With Related Allowance [Member] | Construction [Member]
Impaired Financing Receivable [Abstract]
Average Recorded Investment	0	16	0	18
Interest Income Recognized	0	0	0	0
With Related Allowance [Member] | Land, Farmland, Ag Loans [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	273		273		230
Unpaid Principal Balance	273		273		230
Related Allowance	32		32		68
Average Recorded Investment	275	902	276	243
Interest Income Recognized	3	25	10	9
With Related Allowance [Member] | Residential [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	11,369		11,369		11,107
Unpaid Principal Balance	11,552		11,552		11,473
Related Allowance	608		608		500
Average Recorded Investment	11,494	10,954	11,468	11,756
Interest Income Recognized	107	186	339	194
With Related Allowance [Member] | Commercial and Non-Residential [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	3,232		3,232		3,674
Unpaid Principal Balance	3,281		3,281		3,700
Related Allowance	246		246		369
Average Recorded Investment	3,249	5,544	3,256	8,361
Interest Income Recognized	36	163	104	253
With Related Allowance [Member] | Commercial and Industrial [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	82		82		539
Unpaid Principal Balance	82		82		539
Related Allowance	8		8		25
Average Recorded Investment	86	308	88	377
Interest Income Recognized	2	4	4	12
With Related Allowance [Member] | Multi Family [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	6,643		6,643		4,541
Unpaid Principal Balance	6,643		6,643		4,541
Related Allowance	708		708		416
Average Recorded Investment	6,667	4,577	6,670	4,611
Interest Income Recognized	75	107	252	107
With Related Allowance [Member] | Consumer [Member]
Impaired Financing Receivable [Abstract]
Recorded Investment	392		392		491
Unpaid Principal Balance	392		392		518
Related Allowance	113		113		40
Average Recorded Investment	397	553	433	280
Interest Income Recognized	$ 1	$ 12	$ 5	$ 8