Loans and Allowance for Loan Losses (Troubled loan receivables, by accrual status) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
Nonaccrual	$ 3,363	$ 3,137
Accrual	3,356	4,099
Troubled debt restructurings, total	6,719	7,236
Commercial
Financing Receivable, Impaired [Line Items]
Nonaccrual	1,900	371
Accrual	277	1,071
Troubled debt restructurings, total	2,177	1,442
Commercial real estate
Financing Receivable, Impaired [Line Items]
Nonaccrual	1,463	1,889
Accrual	956	498
Troubled debt restructurings, total	2,419	2,387
Commercial construction
Financing Receivable, Impaired [Line Items]
Nonaccrual	0	46
Accrual	0	295
Troubled debt restructurings, total	0	341
Land and land development loans
Financing Receivable, Impaired [Line Items]
Nonaccrual	0	782
Accrual	1,327	794
Troubled debt restructurings, total	1,327	1,576
Agriculture
Financing Receivable, Impaired [Line Items]
Nonaccrual	0	22
Accrual	291	0
Troubled debt restructurings, total	291	22
Residential real estate
Financing Receivable, Impaired [Line Items]
Nonaccrual	0	0
Accrual	417	1,377
Troubled debt restructurings, total	417	1,377
Consumer
Financing Receivable, Impaired [Line Items]
Nonaccrual	0	27
Accrual	88	64
Troubled debt restructurings, total	$ 88	$ 91