Loans - Individually Evaluated For Impairment By Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
Total impaired loans	$ 14,404		$ 14,404		$ 15,393
Impaired Financing Receivable, Recorded Investment, Total	11,560		11,560		12,131
Impaired Financing Receivable Allocated Loans and Leases	1,493		1,493		897
Impaired Financing Receivable, Average Recorded Investment, Total	11,676	10,926	12,425	9,647
Impaired Financing Receivable, Interest Income, Accrual Method, Total	122	88	299	109
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	6,438		6,438		4,890
Impaired Financing Receivable, with Related Allowance, Recorded Investment	6,271		6,271		4,752
Impaired Financing Receivable with Related Allowance, Allocated Loans and Leases	1,493		1,493		897
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	6,285	4,522	6,361	6,780
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	122	39	299	39
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	7,966		7,966		10,503
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	5,289		5,289		7,379
Impaired Financing Receivable, with No Related Allowance, Allocated Loans and Leases	0		0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	5,391	6,404	6,064	2,867
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0	49	0	70
Originated for portfolio [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance					135
Impaired Financing Receivable, with No Related Allowance, Recorded Investment					135
Impaired Financing Receivable, with No Related Allowance, Allocated Loans and Leases					0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		135		136
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	669		669		796
Impaired Financing Receivable, with Related Allowance, Recorded Investment	669		669		774
Impaired Financing Receivable with Related Allowance, Allocated Loans and Leases	564		564		624
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	672	515	686	1,163
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	8	8	30	8
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	143		143		573
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	128		128		47
Impaired Financing Receivable, with No Related Allowance, Allocated Loans and Leases	0		0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	130	1,248	137	515
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0	7	0	7
Multi-family residential [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	2,117		2,117		94
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,995		1,995		94
Impaired Financing Receivable with Related Allowance, Allocated Loans and Leases	585		585		11
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	1,996	2,278	2,002	3,048
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	61		103
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	2,934		2,934		6,742
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,029		2,029		4,996
Impaired Financing Receivable, with No Related Allowance, Allocated Loans and Leases	0		0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	2,032	787	2,170	262
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0	1	0	1
Commercial [Member] | Non-owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	2,662		2,662		2,823
Impaired Financing Receivable, with Related Allowance, Recorded Investment	2,662		2,662		2,823
Impaired Financing Receivable with Related Allowance, Allocated Loans and Leases	274		274		210
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	2,670	1,379	2,684	1,752
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	40	31	127	31
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	2,645		2,645		2,177
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,839		1,839		1,755
Impaired Financing Receivable, with No Related Allowance, Allocated Loans and Leases	0		0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	1,869	2,236	2,357	796
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0	9	0	9
Commercial [Member] | Owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	401		401		411
Impaired Financing Receivable, with Related Allowance, Recorded Investment	401		401		411
Impaired Financing Receivable with Related Allowance, Allocated Loans and Leases	7		7		20
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	402	350	406	817
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	6		19
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	2,244		2,244		876
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,293		1,293		446
Impaired Financing Receivable, with No Related Allowance, Allocated Loans and Leases	0		0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	1,360	1,314	1,400	438
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0	21	0	21
Commercial [Member] | Land [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	460		460		766
Impaired Financing Receivable, with Related Allowance, Recorded Investment	415		415		650
Impaired Financing Receivable with Related Allowance, Allocated Loans and Leases	16		16		32
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	416		452
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	6		19
Impaired Financing Receivable, with No Related Allowance, Allocated Loans and Leases					0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		684		688
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		11		32
Single-family residential [Member]
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	129		129
Impaired Financing Receivable, with Related Allowance, Recorded Investment	129		129
Impaired Financing Receivable with Related Allowance, Allocated Loans and Leases	47		47
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	129		131
Impaired Financing Receivable, with Related Allowance, Interest Income, Accrual Method	1		1
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance					0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment					0
Impaired Financing Receivable, with No Related Allowance, Allocated Loans and Leases					0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		0		32
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment		$ 0