Loans and Allowance - Corporation's nonaccrual loans (Details 5) (Loans Receivable, USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total nonaccrual loans	$ 11,663	$ 10,850
Nonaccrual loans as a percent of total loans	3.67%	3.45%
Construction / Land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total nonaccrual loans	4,492	4,798
One-to-four family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total nonaccrual loans	3,257	2,687
Multi-family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total nonaccrual loans	1,088	1,104
Nonresidential and agricultural land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total nonaccrual loans	2,419	1,678
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total nonaccrual loans	379	567
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total nonaccrual loans	$ 28	$ 16