Loans - Average Recorded Investment and Interest Income Recognized on Impaired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	$ 155,019	$ 158,807	$ 147,922	$ 175,256
Interest Income Recognized	1,160	1,168	3,840	4,205
Total commercial real estate loans
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	96,516	99,999	92,966	109,725
Interest Income Recognized	677	751	2,333	2,618
Total consumer loans
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	4,275	3,039	4,125	1,855
Interest Income Recognized	43	18	111	47
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	28,892	30,387	27,570	37,229
Interest Income Recognized	232	172	689	831
Commercial real estate
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	76,509	83,045	76,900	91,184
Interest Income Recognized	538	604	1,918	2,173
Construction
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	20,007	16,954	16,066	18,541
Interest Income Recognized	139	147	415	445
Residential mortgage
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	25,336	25,382	23,261	26,447
Interest Income Recognized	208	227	707	709
Home equity
Accounts, Notes, Loans and Financing Receivable
Average Recorded Investment	4,275	3,039	4,125	1,855
Interest Income Recognized	$ 43	$ 18	$ 111	$ 47