Loans and Allowance for Loan Losses - Summary of Troubled Debt Restructurings by Collateral Types (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Modifications [Line Items]
Troubled debt restructuring loans	$ 23,900	$ 26,100
Accruing Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	55	39
Troubled debt restructuring loans	18,744	17,951
Accruing Loans [Member] | Warehouse [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	3	1
Troubled debt restructuring loans	1,692	1,347
Accruing Loans [Member] | Raw Land [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	2	3
Troubled debt restructuring loans	1,337	1,549
Accruing Loans [Member] | Hotel & Motel [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	3	1
Troubled debt restructuring loans	2,318	503
Accruing Loans [Member] | Office [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	4	3
Troubled debt restructuring loans	2,105	1,077
Accruing Loans [Member] | Retail, including Strip Centers [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	6	9
Troubled debt restructuring loans	2,833	6,694
Accruing Loans [Member] | 1-4 Family Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	31	22
Troubled debt restructuring loans	7,651	6,781
Accruing Loans [Member] | Life Insurance Policy [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1
Troubled debt restructuring loans	250
Accruing Loans [Member] | Automobile/Equipment/Inventory [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	4
Troubled debt restructuring loans	508
Accruing Loans [Member] | Unsecured [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1
Troubled debt restructuring loans	50
Non-Accruing Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	5	11
Troubled debt restructuring loans	5,171	8,155
Non-Accruing Loans [Member] | Warehouse [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1
Troubled debt restructuring loans	177
Non-Accruing Loans [Member] | Raw Land [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts		2
Troubled debt restructuring loans		618
Non-Accruing Loans [Member] | Hotel & Motel [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts		1
Troubled debt restructuring loans		2,072
Non-Accruing Loans [Member] | Office [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1
Troubled debt restructuring loans	2,770
Non-Accruing Loans [Member] | Retail, including Strip Centers [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1	1
Troubled debt restructuring loans	1,202	2,665
Non-Accruing Loans [Member] | 1-4 Family Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	2	7
Troubled debt restructuring loans	$ 1,022	$ 2,800