Credit Quality of Loan Portfolio (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60 days	$ 31,135	$ 11,660
61-90 days	278	3,793
> 90 days	54	247
Total past due	31,467	15,700
Non-accrual loans and leases	38,576	47,548
Loans aquired with deteriorated credit quality	9,092	7,200
Current loans	2,485,934	2,460,680
Total loans and leases	2,565,069	2,531,128
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60 days	5,296	2,138
61-90 days	0	212
> 90 days	0	24
Total past due	5,296	2,374
Non-accrual loans and leases	4,012	4,611
Loans aquired with deteriorated credit quality	1,996	1,978
Current loans	333,185	337,745
Total loans and leases	344,489	346,708
Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60 days	0	7
61-90 days	0	68
> 90 days	0	0
Total past due	0	75
Non-accrual loans and leases	0	865
Loans aquired with deteriorated credit quality	0	0
Current loans	1,974	2,481
Total loans and leases	1,974	3,421
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60 days	873	496
61-90 days	217	101
> 90 days	54	14
Total past due	1,144	611
Non-accrual loans and leases	2,388	2,410
Loans aquired with deteriorated credit quality	0	0
Current loans	349,809	353,969
Total loans and leases	353,341	356,990
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60 days	2,148	0
61-90 days	0	0
> 90 days	0	0
Total past due	2,148	0
Non-accrual loans and leases	5,826	6,332
Loans aquired with deteriorated credit quality	331	332
Current loans	142,294	145,269
Total loans and leases	150,599	151,933
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60 days	10,997	2,020
61-90 days	0	0
> 90 days	0	0
Total past due	10,997	2,020
Non-accrual loans and leases	12,353	11,843
Loans aquired with deteriorated credit quality	2,251	949
Current loans	462,201	442,076
Total loans and leases	487,802	456,888
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60 days	6,362	1,556
61-90 days	0	1,809
> 90 days	0	209
Total past due	6,362	3,574
Non-accrual loans and leases	5,346	13,681
Loans aquired with deteriorated credit quality	4,514	3,941
Current loans	549,598	550,314
Total loans and leases	565,820	571,510
Residential Real Estate Portfolio Segment | Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60 days	5,459	5,443
61-90 days	61	1,603
> 90 days	0	0
Total past due	5,520	7,046
Non-accrual loans and leases	5,393	4,681
Loans aquired with deteriorated credit quality	0	0
Current loans	527,433	511,637
Total loans and leases	538,346	523,364
Residential Real Estate Portfolio Segment | Residential Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60 days	0	0
61-90 days	0	0
> 90 days	0	0
Total past due	0	0
Non-accrual loans and leases	3,258	3,125
Loans aquired with deteriorated credit quality	0	0
Current loans	119,440	117,189
Total loans and leases	$ 122,698	$ 120,314