Loans - Impaired Financing Receivables with Related and not Related Allowances (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Financing Receivable, Impaired [Line Items]
Average Recorded Investment, Total	$ 18,403	$ 24,193	$ 18,371	$ 25,418
Interest Income Recognized, Total	4	3	13	7
Cash Basis Interest Recognized, Total	4	3	13	7
Commercial, Industrial, and Agricultural [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment, Related Allowance	4,318	1,459	4,438	1,621
Interest Income Recognized, Related Allowance	1	1	2	1
Cash Basis Interest Recognized, Related Allowance	1	1	2	1
Average Recorded Investment, No Related Allowance	2,234	2,172	2,167	2,184
Interest Income Recognized, No Related Allowance	0	0	0	0
Cash Basis Interest Recognized, No Related Allowance	0	0	0	0
Commercial Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment, Related Allowance	5,402	5,787	5,416	6,009
Interest Income Recognized, Related Allowance	0	0	0	3
Cash Basis Interest Recognized, Related Allowance	0	0	0	3
Average Recorded Investment, No Related Allowance	6,249	14,637	6,217	15,270
Interest Income Recognized, No Related Allowance	0	0	0	0
Cash Basis Interest Recognized, No Related Allowance	0	0	0	0
Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment, Related Allowance	200	62	133	191
Interest Income Recognized, Related Allowance	3	2	11	3
Cash Basis Interest Recognized, Related Allowance	3	2	11	3
Average Recorded Investment, No Related Allowance	0	76	0	143
Interest Income Recognized, No Related Allowance	0	0	0	0
Cash Basis Interest Recognized, No Related Allowance	$ 0	$ 0	$ 0	$ 0