Troubled Debt Restructurings (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013 Loan	Dec. 31, 2012 Loan
Financing Receivable, Modifications [Line Items]
Number of Loans	18	15
Pre-Modification Outstanding Recorded Investment	$ 33,616	$ 31,008
Post-Modification Outstanding Recorded Investment	32,390	30,684
End of Period Balance	27,232	27,232
Performing
Financing Receivable, Modifications [Line Items]
Number of Loans	9	9
Pre-Modification Outstanding Recorded Investment	26,190	22,080
Post-Modification Outstanding Recorded Investment	26,190	22,080
End of Period Balance	33,000	21,595
Performing | Land development loans
Financing Receivable, Modifications [Line Items]
Number of Loans	1	1
Pre-Modification Outstanding Recorded Investment	1,429	1,429
Post-Modification Outstanding Recorded Investment	1,429	1,429
End of Period Balance	1,394	1,412
Performing | Commercial loans
Financing Receivable, Modifications [Line Items]
Number of Loans	2	4
Pre-Modification Outstanding Recorded Investment	8,310	9,754
Post-Modification Outstanding Recorded Investment	8,310	9,754
End of Period Balance	8,273	9,334
Performing | All other | Commercial real estate
Financing Receivable, Modifications [Line Items]
Number of Loans	6	4
Pre-Modification Outstanding Recorded Investment	16,451	10,897
Post-Modification Outstanding Recorded Investment	16,451	10,897
End of Period Balance	12,693	10,849
Nonperforming
Financing Receivable, Modifications [Line Items]
Number of Loans	9	6
Pre-Modification Outstanding Recorded Investment	7,426	8,928
Post-Modification Outstanding Recorded Investment	6,200	8,604
End of Period Balance	4,879	5,637
Nonperforming | Land development loans
Financing Receivable, Modifications [Line Items]
Number of Loans	1
Pre-Modification Outstanding Recorded Investment	439
Post-Modification Outstanding Recorded Investment	439
End of Period Balance	414
Nonperforming | Commercial loans
Financing Receivable, Modifications [Line Items]
Number of Loans	6	3
Pre-Modification Outstanding Recorded Investment	4,944	1,943
Post-Modification Outstanding Recorded Investment	3,830	1,855
End of Period Balance	2,599	1,753
Nonperforming | All other | Commercial real estate
Financing Receivable, Modifications [Line Items]
Number of Loans		2
Pre-Modification Outstanding Recorded Investment		6,814
Post-Modification Outstanding Recorded Investment		6,685
End of Period Balance		3,825
Nonperforming | Owner occupied | Commercial real estate
Financing Receivable, Modifications [Line Items]
Number of Loans	1
Pre-Modification Outstanding Recorded Investment	1,872
Post-Modification Outstanding Recorded Investment	1,867
End of Period Balance	1,811
Nonperforming | Single-family | Residential mortgage loans
Financing Receivable, Modifications [Line Items]
Number of Loans	1	1
Pre-Modification Outstanding Recorded Investment	171	171
Post-Modification Outstanding Recorded Investment	64	64
End of Period Balance	$ 55	$ 59