Individually Impaired Loans 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]
Unpaid Principal Balance	$ 37,680	$ 43,630	$ 37,680	$ 43,630	$ 38,326
Recorded Investment	34,503	39,173	34,503	39,173	35,261
Allowance for Loan Losses Allocated	6,254	7,762	6,254	7,762	7,443
Average Recorded Investment	35,515	34,682	36,647	29,851
Interest Income Recognized	218	288	662	612
Interest Received	211	221	601	513
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,118		1,118		917
Allowance for Loan Losses Allocated	317		317		224
Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	8,500		8,500		6,100
Allowance for Loan Losses Allocated	1,729		1,729		477
Nonresidential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	19,111		19,111		20,390
Allowance for Loan Losses Allocated	2,993		2,993		2,994
Construction [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	5,774		5,774		7,854
Allowance for Loan Losses Allocated	1,215		1,215		3,748
Impaired Financing Receivables with No Related Allowance [Member] \| Commercial [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	30	349	30	349	350
Recorded Investment	30	310	30	310	310
Allowance for Loan Losses Allocated	0	0	0	0	0
Average Recorded Investment	170	371	263	351
Interest Income Recognized	0	0	0	0
Interest Received	0	0	0	0
Impaired Financing Receivables with No Related Allowance [Member] \| Residential Real Estate [Member] \| Home Equity Line of Credit [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	50	0	50	0	50
Recorded Investment	50	0	50	0	50
Allowance for Loan Losses Allocated	0	0	0	0	0
Average Recorded Investment	50		50	0
Interest Income Recognized	0		0	0
Interest Received	0		0	0
Impaired Financing Receivables with No Related Allowance [Member] \| Residential Real Estate [Member] \| Multi Family [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	379	0	379	0	538
Recorded Investment	48	0	48	0	538
Allowance for Loan Losses Allocated	0	0	0	0	0
Average Recorded Investment	24	0	273	17
Interest Income Recognized	0	0	0	0
Interest Received	0	0	0	0
Impaired Financing Receivables with No Related Allowance [Member] \| Residential Real Estate [Member] \| Residential Real Estate Other Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	2,869	2,121	2,869	2,121	1,703
Recorded Investment	2,626	2,121	2,626	2,121	1,703
Allowance for Loan Losses Allocated	0	0	0	0	0
Average Recorded Investment	2,336	2,325	2,094	1,288
Interest Income Recognized	0	0	0	0
Interest Received	0	0	0	0
Impaired Financing Receivables with No Related Allowance [Member] \| Nonresidential Real Estate [Member] \| Commercial Mortgage Loans, Owner Occupied [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	802	1,011	802	1,011	1,101
Recorded Investment	792	955	792	955	1,101
Allowance for Loan Losses Allocated	0	0	0	0	0
Average Recorded Investment	490	587	698	503
Interest Income Recognized	0	0	0	0
Interest Received	0	0	0	0
Impaired Financing Receivables with No Related Allowance [Member] \| Nonresidential Real Estate [Member] \| Commercial Mortgage Loans, Non Owner Occupied [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	6,206	897	6,206	897	2,122
Recorded Investment	5,701	897	5,701	897	2,116
Allowance for Loan Losses Allocated	0	0	0	0	0
Average Recorded Investment	3,797	1,044	2,848	848
Interest Income Recognized	0	0	0	0
Interest Received	0	0	0	0
Impaired Financing Receivables with No Related Allowance [Member] \| Construction [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	809	2,036	809	2,036	356
Recorded Investment	509	889	509	889	319
Allowance for Loan Losses Allocated	0	0	0	0	0
Average Recorded Investment	432	909	256	559
Interest Income Recognized	0	0	0	0
Interest Received	0	0	0	0
Impaired Financing Receivables with Related Allowance [Member] \| Commercial [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	1,088	1,379	1,088	1,379	733
Recorded Investment	1,088	1,379	1,088	1,379	607
Allowance for Loan Losses Allocated	317	504	317	504	224
Average Recorded Investment	823	2,370	950	1,959
Interest Income Recognized	4	10	7	17
Interest Received	4	5	5	9
Impaired Financing Receivables with Related Allowance [Member] \| Residential Real Estate [Member] \| Home Equity Line of Credit [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	1,488	0	1,488	0	0
Recorded Investment	1,488	0	1,488	0	0
Allowance for Loan Losses Allocated	1,341	0	1,341	0	0
Average Recorded Investment	813	0	339	0
Interest Income Recognized	12	0	12	0
Interest Received	12	0	12	0
Impaired Financing Receivables with Related Allowance [Member] \| Residential Real Estate [Member] \| Multi Family [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	1,324	868	1,324	868	0
Recorded Investment	1,324	868	1,324	868	0
Allowance for Loan Losses Allocated	243	291	243	291	0
Average Recorded Investment	1,554	869	815	922
Interest Income Recognized	11	14	22	42
Interest Received	11	9	22	28
Impaired Financing Receivables with Related Allowance [Member] \| Residential Real Estate [Member] \| Residential Real Estate Other Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	3,109	2,869	3,109	2,869	3,859
Recorded Investment	2,964	2,850	2,964	2,850	3,809
Allowance for Loan Losses Allocated	145	433	145	433	477
Average Recorded Investment	3,309	2,755	3,557	2,441
Interest Income Recognized	31	18	76	54
Interest Received	24	17	64	51
Impaired Financing Receivables with Related Allowance [Member] \| Nonresidential Real Estate [Member] \| Commercial Mortgage Loans, Owner Occupied [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	8,544	9,471	8,544	9,471	10,771
Recorded Investment	8,543	9,348	8,543	9,348	9,798
Allowance for Loan Losses Allocated	2,651	1,093	2,651	1,093	1,477
Average Recorded Investment	8,774	5,123	9,081	2,884
Interest Income Recognized	81	80	239	81
Interest Received	81	25	237	26
Impaired Financing Receivables with Related Allowance [Member] \| Nonresidential Real Estate [Member] \| Commercial Mortgage Loans, Non Owner Occupied [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	4,595	13,667	4,595	13,667	8,476
Recorded Investment	4,074	11,830	4,074	11,830	7,375
Allowance for Loan Losses Allocated	342	2,185	342	2,185	1,517
Average Recorded Investment	6,449	9,870	7,406	10,044
Interest Income Recognized	34	90	143	215
Interest Received	34	90	106	210
Impaired Financing Receivables with Related Allowance [Member] \| Construction [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	6,387	8,962	6,387	8,962	8,267
Recorded Investment	5,266	7,726	5,266	7,726	7,535
Allowance for Loan Losses Allocated	1,215	3,256	1,215	3,256	3,748
Average Recorded Investment	6,494	8,459	8,017	8,035
Interest Income Recognized	45	76	163	203
Interest Received	$ 45	$ 75	$ 155	$ 189