Loans and Allowance - Corporation's nonaccrual loans (Details 5) (Loans Receivable, USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total nonaccrual loans	$ 10,874	$ 10,850
Construction / Land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total nonaccrual loans	4,381	4,798
One-to-four family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total nonaccrual loans	2,645	2,687
Multi-family residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total nonaccrual loans	1,091	1,104
Nonresidential real estate and agricultural land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total nonaccrual loans	2,187	1,678
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total nonaccrual loans	561	567
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total nonaccrual loans	$ 9	$ 16