Credit Risk Profile Based on Payment Activity (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	$ 1,184,142	$ 1,277,090	$ 1,307,586
Consumer Portfolio Segment
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	45,734	50,978	53,600
Consumer Portfolio Segment | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	45,075	50,327
Consumer Portfolio Segment | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	$ 659	$ 651