Loans on Nonaccrual Status by Portfolio Type (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	$ 8,725	$ 17,655
Commercial loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	3,595	6,846
Commercial real estate | Owner occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	1,811	3,232
Commercial real estate | All other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	2,117	6,424
Residential mortgage loans | Single-family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	788	839
Land development loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	$ 414	$ 314