Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Loans receivable for which there is a related allowance for credit losses determined in accordance with ASC 310-10/Statement No. 114	$ 4,944	$ 5,339
Unpaid Principal Balance	26,220	31,014
Other impaired loans	15,755	20,508
Total impaired loans	20,699	25,847
Average monthly balance of impaired loans	19,161	29,171
Related Allowance	2,135	2,385
Average Recorded Investment	23,460	28,430
Commercial
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	17,991	22,610
Total impaired loans	13,936	18,530
Related Allowance	1,320	1,309
Average Recorded Investment	15,964	20,570
Consumer
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	6,456	6,540
Total impaired loans	5,191	5,586
Related Allowance	815	962
Average Recorded Investment	5,824	6,063
Owner Occupied Residential Real Estate Loans
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	1,773	1,864
Total impaired loans	1,572	1,731
Related Allowance		114
Average Recorded Investment	1,672	1,797
Impaired Financing Receivables with No Related Allowance | Commercial Real Estate
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	9,929	14,778
Total impaired loans	8,499	13,273
Average Recorded Investment	9,214	14,025
Impaired Financing Receivables with No Related Allowance | Commercial Non Real Estate
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	2,353	2,004
Total impaired loans	2,002	1,680
Average Recorded Investment	2,178	1,842
Impaired Financing Receivables with No Related Allowance | Other Consumer
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	3,989	4,611
Total impaired loans	3,036	3,696
Average Recorded Investment	3,513	4,154
Impaired Financing Receivables with No Related Allowance | Consumer Home Equity
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	689	566
Total impaired loans	646	536
Average Recorded Investment	667	551
Impaired Financing Receivables with No Related Allowance | Residential 1-4 family | Residential Real Estate
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	1,773	1,448
Total impaired loans	1,572	1,323
Average Recorded Investment	1,672	1,385
Impaired Financing Receivables with Related Allowance | Commercial Real Estate
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	5,597	5,622
Total impaired loans	3,340	3,388
Related Allowance	1,273	1,260
Average Recorded Investment	4,468	4,505
Impaired Financing Receivables with Related Allowance | Commercial Non Real Estate
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	112	206
Total impaired loans	95	189
Related Allowance	47	49
Average Recorded Investment	104	198
Impaired Financing Receivables with Related Allowance | Other Consumer
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	1,778	1,363
Total impaired loans	1,509	1,354
Related Allowance	815	962
Average Recorded Investment	1,644	1,358
Impaired Financing Receivables with Related Allowance | Residential 1-4 family | Residential Real Estate
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance		416
Total impaired loans		408
Related Allowance		114
Average Recorded Investment		$ 412