Troubled Debt Restructurings (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012 Loan	Dec. 31, 2011
Financing Receivable, Modifications [Line Items]
Number of loans	13
Pre-Modification Outstanding Recorded Investment	$ 23,587
Post Modification Outstanding Recorded Investment	23,119
End of Period Balance	22,360	4,214
Nonperforming
Financing Receivable, Modifications [Line Items]
Number of loans	6	1
Pre-Modification Outstanding Recorded Investment	7,407	4,942
Post Modification Outstanding Recorded Investment	6,939	4,818
End of Period Balance	6,180	4,214
Nonperforming | Commercial loans
Financing Receivable, Modifications [Line Items]
Number of loans	4
Pre-Modification Outstanding Recorded Investment	2,294
Post Modification Outstanding Recorded Investment	2,057
End of Period Balance	2,045
Nonperforming | Residential mortgage loans - single family
Financing Receivable, Modifications [Line Items]
Number of loans	1
Pre-Modification Outstanding Recorded Investment	171
Post Modification Outstanding Recorded Investment	64
End of Period Balance	64
Nonperforming | Commercial real estate | All other
Financing Receivable, Modifications [Line Items]
Number of loans	1	1
Pre-Modification Outstanding Recorded Investment	4,942	4,942
Post Modification Outstanding Recorded Investment	4,818	4,818
End of Period Balance	4,071	4,214
Performing
Financing Receivable, Modifications [Line Items]
Number of loans	7
Pre-Modification Outstanding Recorded Investment	16,180
Post Modification Outstanding Recorded Investment	16,180
End of Period Balance	16,180
Performing | Commercial loans
Financing Receivable, Modifications [Line Items]
Number of loans	3
Pre-Modification Outstanding Recorded Investment	9,280
Post Modification Outstanding Recorded Investment	9,280
End of Period Balance	9,280
Performing | Land development loans
Financing Receivable, Modifications [Line Items]
Number of loans	1
Pre-Modification Outstanding Recorded Investment	1,429
Post Modification Outstanding Recorded Investment	1,429
End of Period Balance	1,429
Performing | Commercial real estate | All other
Financing Receivable, Modifications [Line Items]
Number of loans	3
Pre-Modification Outstanding Recorded Investment	5,471
Post Modification Outstanding Recorded Investment	5,471
End of Period Balance	$ 5,471