Activity in Allowance for Loan and Lease Losses by Respective Loan Portfolio Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of year			$ 49,426	$ 62,135	$ 62,135
Provision (credit)	1,585	1,151	2,249	2,666	1,428
Charge-offs			(7,343)		(16,505)
Recoveries			933	699	2,368
Net charge-offs			(6,410)	(9,555)	(14,137)
Balance at end of period	45,265	55,246	45,265	55,246	49,426
Total loans and leases	2,475,078		2,475,078		2,239,692
Allowance for loans and leases to total loans and leases ratio	1.83%		1.83%		2.21%
Balance of loans specifically evaluated for impairment	57,578		57,578		67,575
Allowance for loans specifically evaluated for impairment	4,886		4,886		7,791
Specific allowance to specific loans ratio	8.49%		8.49%		11.53%
Balance of loans collectively evaluated	2,417,500		2,417,500		2,172,117
Allowance for loans collectively evaluated	40,379		40,379		41,635
Collective allowance to collective loans ratio			1.67%		1.92%
Commercial Business
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of year			6,727	12,870	12,870
Provision (credit)			(1,697)		(4,252)
Charge-offs			(354)		(2,565)
Recoveries			578		674
Net charge-offs			224		(1,891)
Balance at end of period	5,254		5,254		6,727
Total loans and leases	334,040		334,040		260,327
Allowance for loans and leases to total loans and leases ratio	1.57%		1.57%		2.58%
Balance of loans specifically evaluated for impairment	7,739		7,739		9,092
Allowance for loans specifically evaluated for impairment	753		753		1,037
Specific allowance to specific loans ratio	9.73%		9.73%		11.41%
Balance of loans collectively evaluated	326,301		326,301		251,235
Allowance for loans collectively evaluated	4,501		4,501		5,690
Collective allowance to collective loans ratio			1.38%		2.26%
Leases
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of year			795	667	667
Provision (credit)			(236)		1,182
Charge-offs			(6)		(1,072)
Recoveries			4		18
Net charge-offs			(2)		(1,054)
Balance at end of period	557		557		795
Total loans and leases	5,618		5,618		6,954
Allowance for loans and leases to total loans and leases ratio	9.91%		9.91%		11.43%
Balance of loans collectively evaluated	5,618		5,618		6,954
Allowance for loans collectively evaluated	557		557		795
Collective allowance to collective loans ratio			9.91%		11.43%
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of year			4,873	4,231	4,231
Provision (credit)			(25)		3,173
Charge-offs			(697)		(2,740)
Recoveries			121		209
Net charge-offs			(576)		(2,531)
Balance at end of period	4,272		4,272		4,873
Total loans and leases	357,534		357,534		360,080
Allowance for loans and leases to total loans and leases ratio	1.19%		1.19%		1.35%
Balance of loans specifically evaluated for impairment	34		34		35
Balance of loans collectively evaluated	357,500		357,500		360,045
Allowance for loans collectively evaluated	4,272		4,272		4,873
Collective allowance to collective loans ratio			1.19%		1.35%
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of year			6,664	18,241	18,241
Provision (credit)			(101)		(11,035)
Charge-offs			(1,076)		(1,780)
Recoveries			59		1,238
Net charge-offs			(1,017)		(542)
Balance at end of period	5,546		5,546		6,664
Total loans and leases	151,620		151,620		160,946
Allowance for loans and leases to total loans and leases ratio	3.66%		3.66%		4.14%
Balance of loans specifically evaluated for impairment	13,055		13,055		18,701
Allowance for loans specifically evaluated for impairment	973		973		7
Specific allowance to specific loans ratio	0.00%		0.00%		0.04%
Balance of loans collectively evaluated	138,565		138,565		142,245
Allowance for loans collectively evaluated	4,573		4,573		6,657
Collective allowance to collective loans ratio			3.30%		4.68%
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of year			8,248	4,793	4,793
Provision (credit)			4,979		4,320
Charge-offs			(3,457)		(868)
Recoveries			98		3
Net charge-offs			(3,359)		(865)
Balance at end of period	9,868		9,868		8,248
Total loans and leases	443,237		443,237		371,948
Allowance for loans and leases to total loans and leases ratio	2.23%		2.23%		2.22%
Balance of loans specifically evaluated for impairment	14,143		14,143		16,964
Allowance for loans specifically evaluated for impairment	276		276		3,380
Specific allowance to specific loans ratio	1.95%		1.95%		19.92%
Balance of loans collectively evaluated	429,094		429,094		354,984
Allowance for loans collectively evaluated	9,592		9,592		4,868
Collective allowance to collective loans ratio			2.24%		1.37%
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of year			7,329	8,177	8,177
Provision (credit)			160		(361)
Charge-offs			(493)		(487)
Recoveries			9
Net charge-offs			(484)		(487)
Balance at end of period	7,005		7,005		7,329
Total loans and leases	579,812		579,812		522,076
Allowance for loans and leases to total loans and leases ratio	1.21%		1.21%		1.40%
Balance of loans specifically evaluated for impairment	16,970		16,970		15,416
Allowance for loans specifically evaluated for impairment	1,336		1,336		1,772
Specific allowance to specific loans ratio	7.87%		7.87%		11.49%
Balance of loans collectively evaluated	562,842		562,842		506,660
Allowance for loans collectively evaluated	5,669		5,669		5,557
Collective allowance to collective loans ratio			1.01%		1.10%
Residential Real Estate Portfolio Segment | Residential Mortgage
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of year			10,583	10,396	10,396
Provision (credit)			284		5,144
Charge-offs			(1,193)		(5,178)
Recoveries			60		221
Net charge-offs			(1,133)		(4,957)
Balance at end of period	9,734		9,734		10,583
Total loans and leases	472,426		472,426		448,662
Allowance for loans and leases to total loans and leases ratio	2.06%		2.06%		2.36%
Balance of loans specifically evaluated for impairment	4,896		4,896		5,108
Allowance for loans specifically evaluated for impairment	1,389		1,389		769
Specific allowance to specific loans ratio	28.37%		28.37%		15.05%
Balance of loans collectively evaluated	467,530		467,530		443,554
Allowance for loans collectively evaluated	8,345		8,345		9,814
Collective allowance to collective loans ratio			1.78%		2.21%
Residential Real Estate Portfolio Segment | Residential Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of year			4,207	2,760	2,760
Provision (credit)			(1,115)		3,257
Charge-offs			(67)		(1,815)
Recoveries			4		5
Net charge-offs			(63)		(1,810)
Balance at end of period	3,029		3,029		4,207
Total loans and leases	130,791		130,791		108,699
Allowance for loans and leases to total loans and leases ratio	2.32%		2.32%		3.87%
Balance of loans specifically evaluated for impairment	741		741		2,259
Allowance for loans specifically evaluated for impairment	159		159		826
Specific allowance to specific loans ratio	21.46%		21.46%		36.56%
Balance of loans collectively evaluated	130,050		130,050		106,440
Allowance for loans collectively evaluated	$ 2,870		$ 2,870		$ 3,381
Collective allowance to collective loans ratio			2.21%		3.18%