Additional Information with Respect to Impaired Loans, by Portfolio Type (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2012		Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 38,356		$ 18,395
Average Recorded Investment	27,600		27,500
Commercial loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	20,366		5,139
Unpaid Principal Balance	22,442		5,888
Related Allowance	4,049	[1]	1,648	[1]
Average Recorded Investment	9,402		3,117
Interest Income Recognized	432		241
Consumer loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment			32
Commercial real estate | Owner occupied
Financing Receivable, Impaired [Line Items]
Recorded Investment	6,919		5,599
Unpaid Principal Balance	7,400		5,599
Related Allowance			659	[1]
Average Recorded Investment	6,848		7,636
Interest Income Recognized	12		388
Commercial real estate | All other
Financing Receivable, Impaired [Line Items]
Recorded Investment	9,542		4,310
Unpaid Principal Balance	10,243		4,914
Related Allowance	189	[1]	347	[1]
Average Recorded Investment	8,528		12,701
Interest Income Recognized	261		3
Residential mortgage loans | Multi-family
Financing Receivable, Impaired [Line Items]
Recorded Investment			180
Unpaid Principal Balance			180
Related Allowance			129	[1]
Average Recorded Investment	90		45
Interest Income Recognized			14
Residential mortgage loans | Residential mortgage loans - single family
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,001		570
Unpaid Principal Balance	1,125		581
Average Recorded Investment	1,063		1,063
Interest Income Recognized	15		15
Construction loans
Financing Receivable, Impaired [Line Items]
Recorded Investment			2,047
Unpaid Principal Balance			2,215
Average Recorded Investment	1,024		2,225
Land development loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	528		550
Unpaid Principal Balance	554		554
Average Recorded Investment	652		632
Interest Income Recognized			11
With no related allowance recorded | Commercial loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	8,082		1,636
Unpaid Principal Balance	10,102		2,361
Average Recorded Investment	4,170		1,395
Interest Income Recognized	164		38
With no related allowance recorded | Consumer loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment			32
With no related allowance recorded | Commercial real estate | Owner occupied
Financing Receivable, Impaired [Line Items]
Recorded Investment	6,919		3,583
Unpaid Principal Balance	7,400		3,583
Average Recorded Investment	5,883		4,621
Interest Income Recognized	12		340
With no related allowance recorded | Commercial real estate | All other
Financing Receivable, Impaired [Line Items]
Recorded Investment	5,471		96
Unpaid Principal Balance	5,471		96
Average Recorded Investment	4,350		3,420
Interest Income Recognized	163		3
With no related allowance recorded | Residential mortgage loans | Multi-family
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	45
With no related allowance recorded | Residential mortgage loans | Residential mortgage loans - single family
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,001		570
Unpaid Principal Balance	1,125		581
Average Recorded Investment	1,063		790
Interest Income Recognized	15		15
With no related allowance recorded | Construction loans
Financing Receivable, Impaired [Line Items]
Recorded Investment			2,047
Unpaid Principal Balance			2,215
Average Recorded Investment	512		621
With no related allowance recorded | Land development loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	528		550
Unpaid Principal Balance	554		554
Average Recorded Investment	652		632
Interest Income Recognized			11
With an allowance recorded | Commercial loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	12,284		3,503
Unpaid Principal Balance	12,340		3,527
Related Allowance	4,049	[1]	1,648	[1]
Average Recorded Investment	5,232		1,722
Interest Income Recognized	268		203
With an allowance recorded | Commercial real estate | Owner occupied
Financing Receivable, Impaired [Line Items]
Recorded Investment			2,016
Unpaid Principal Balance			2,016
Related Allowance			659	[1]
Average Recorded Investment	965		3,015
Interest Income Recognized			48
With an allowance recorded | Commercial real estate | All other
Financing Receivable, Impaired [Line Items]
Recorded Investment	4,071		4,214
Unpaid Principal Balance	4,772		4,818
Related Allowance	189	[1]	347	[1]
Average Recorded Investment	4,178		9,281
Interest Income Recognized	98
With an allowance recorded | Residential mortgage loans | Multi-family
Financing Receivable, Impaired [Line Items]
Recorded Investment			180
Unpaid Principal Balance			180
Related Allowance			129	[1]
Average Recorded Investment	45		45
Interest Income Recognized			14
With an allowance recorded | Residential mortgage loans | Residential mortgage loans - single family
Financing Receivable, Impaired [Line Items]
Average Recorded Investment			273
With an allowance recorded | Construction loans
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 512		$ 1,604

[1] When the discounted cash flows and collateral value or market price equals or exceeds the recorded investment in the loan, then the loan does not require an allowance. This typically occurs when the impaired loans have been partially charged-off and/or there have been interest payments received and applied to the loan balance.