Credit Quality of Loan Portfolio (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60 days	$ 12,637	$ 22,036
61-90 days	3,269	4,258
> 90 days	305	577
Total past due	16,211	26,871
Non-accrual loans and leases	49,284	71,680
Current loans	2,403,490	2,141,141
Total loans and leases	2,468,985	2,239,692
Commercial Loan
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60 days	3,400	1,467
61-90 days	457	62
> 90 days	44
Total past due	3,901	1,529
Non-accrual loans and leases	4,919	7,226
Current loans	313,267	251,572
Total loans and leases	322,087	260,327
Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60 days	22	7
61-90 days	2
> 90 days	127	2
Total past due	151	9
Non-accrual loans and leases	834	853
Current loans	3,248	6,092
Total loans and leases	4,233	6,954
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60 days	1,337	467
61-90 days	533	20
> 90 days	18	165
Total past due	1,888	652
Non-accrual loans and leases	1,607	1,786
Current loans	350,504	357,642
Total loans and leases	353,999	360,080
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60 days		717
Total past due		717
Non-accrual loans and leases	8,957	18,702
Current loans	124,050	141,527
Total loans and leases	133,007	160,946
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60 days	328	10,723
61-90 days	90
Total past due	418	10,723
Non-accrual loans and leases	12,345	16,963
Current loans	434,773	344,262
Total loans and leases	447,536	371,948
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60 days	3,283	1,677
61-90 days	210	2,537
Total past due	3,493	4,214
Non-accrual loans and leases	13,742	14,709
Current loans	562,476	503,153
Total loans and leases	579,711	522,076
Residential Real Estate Portfolio Segment | Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60 days	4,267	5,246
61-90 days	1,977	1,639
> 90 days	116	167
Total past due	6,360	7,052
Non-accrual loans and leases	3,644	5,722
Current loans	489,802	435,888
Total loans and leases	499,806	448,662
Residential Real Estate Portfolio Segment | Residential Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
31-60 days		1,732
> 90 days		243
Total past due		1,975
Non-accrual loans and leases	3,236	5,719
Current loans	125,370	101,005
Total loans and leases	$ 128,606	$ 108,699