Analysis of Impaired Loans by Class (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance	$ 46,187	$ 34,471
Recorded Investment with No Allowance	9,941	20,935
Recorded Investment with Allowance	20,776	5,374
Total Recorded Investment	30,717	26,309
Related Allowance	4,713	2,174
Average Recorded Investment	27,002	25,995
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance	29,380	22,453
Recorded Investment with No Allowance	2,556	12,119
Recorded Investment with Allowance	12,279	2,938
Total Recorded Investment	14,835	15,057
Related Allowance	3,301	1,393
Average Recorded Investment	14,831	13,287
Commercial - credit card [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance
Recorded Investment with No Allowance
Recorded Investment with Allowance
Total Recorded Investment
Related Allowance
Average Recorded Investment
Real estate - construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance	1,409	276
Recorded Investment with No Allowance	731	276
Recorded Investment with Allowance	416
Total Recorded Investment	1,147	276
Related Allowance	222
Average Recorded Investment	1,249	118
Real estate - commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance	13,845	9,334
Recorded Investment with No Allowance	5,339	6,777
Recorded Investment with Allowance	8,081	2,213
Total Recorded Investment	13,420	8,990
Related Allowance	1,190	733
Average Recorded Investment	9,752	9,925
Real estate - residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance	1,519	2,357
Recorded Investment with No Allowance	1,285	1,714
Recorded Investment with Allowance		223
Total Recorded Investment	1,285	1,937
Related Allowance		48
Average Recorded Investment	1,131	2,622
Real estate - Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance
Recorded Investment with No Allowance
Recorded Investment with Allowance
Total Recorded Investment
Related Allowance
Average Recorded Investment
Consumer - credit card [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance
Recorded Investment with No Allowance
Recorded Investment with Allowance
Total Recorded Investment
Related Allowance
Average Recorded Investment
Consumer - other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance	34	51
Recorded Investment with No Allowance	30	49
Recorded Investment with Allowance
Total Recorded Investment	30	49
Related Allowance
Average Recorded Investment	39	43
Leases [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance
Recorded Investment with No Allowance
Recorded Investment with Allowance
Total Recorded Investment
Related Allowance
Average Recorded Investment