Credit Quality of Loan Portfolio by Segment (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Non-accrual loans and leases	$ 38,576	$ 47,548
Loans and leases 90 days past due	54	247
Restructured loans and leases	10,839	10,110
Total non-performing loans and leases	49,469	57,905
Other real estate owned	5,250	5,926
Total non-performing assets	54,719	63,831
Commercial
Financing Receivable, Recorded Investment [Line Items]
Non-accrual loans and leases	4,012	4,611
Loans and leases 90 days past due	0	24
Restructured loans and leases	3,875	4,373
Total non-performing loans and leases	7,887	9,008
Other real estate owned	1,829	1,829
Total non-performing assets	9,716	10,837
Leases
Financing Receivable, Recorded Investment [Line Items]
Non-accrual loans and leases	0	865
Loans and leases 90 days past due	0	0
Restructured loans and leases	0	0
Total non-performing loans and leases	0	865
Other real estate owned	0	0
Total non-performing assets	0	865
Consumer
Financing Receivable, Recorded Investment [Line Items]
Non-accrual loans and leases	2,388	2,410
Loans and leases 90 days past due	54	14
Restructured loans and leases	31	31
Total non-performing loans and leases	2,473	2,455
Other real estate owned	0	0
Total non-performing assets	2,473	2,455
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Non-accrual loans and leases	5,826	6,332
Loans and leases 90 days past due	0	0
Restructured loans and leases	0	0
Total non-performing loans and leases	5,826	6,332
Other real estate owned	0	0
Total non-performing assets	5,826	6,332
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate
Financing Receivable, Recorded Investment [Line Items]
Non-accrual loans and leases	12,353	11,843
Loans and leases 90 days past due	0	0
Restructured loans and leases	852	0
Total non-performing loans and leases	13,205	11,843
Other real estate owned	80	220
Total non-performing assets	13,285	12,063
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Non-accrual loans and leases	5,346	13,681
Loans and leases 90 days past due	0	209
Restructured loans and leases	1,897	1,503
Total non-performing loans and leases	7,243	15,393
Other real estate owned	2,223	2,396
Total non-performing assets	9,466	17,789
Residential Real Estate Portfolio Segment | Residential Mortgage
Financing Receivable, Recorded Investment [Line Items]
Non-accrual loans and leases	5,393	4,681
Loans and leases 90 days past due	0	0
Restructured loans and leases	4,184	4,203
Total non-performing loans and leases	9,577	8,884
Other real estate owned	1,118	1,401
Total non-performing assets	10,695	10,285
Residential Real Estate Portfolio Segment | Residential Construction
Financing Receivable, Recorded Investment [Line Items]
Non-accrual loans and leases	3,258	3,125
Loans and leases 90 days past due	0	0
Restructured loans and leases	0	0
Total non-performing loans and leases	3,258	3,125
Other real estate owned	0	80
Total non-performing assets	$ 3,258	$ 3,205