Loans and Allowance for Loan Losses (Nonaccrual Status) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest lost on nonaccrual loans	$ 5,400,000	$ 11,700,000
Loans on nonaccrual status	79,200,000	103,000,000
Days after due date in which loans are considered past due	30 days
Days after due date in which loans are put on nonaccrual status	90 days
Loans held for investment on nonaccrual status	79,242,000	98,444,000
Loans more than 90 days delinquent, still on accrual	24,060,000	11,995,000
Net loans held for investment	1,147,721,000	1,178,175,000
Nonperforming [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment on nonaccrual status	79,242,000	98,444,000
Loans more than 90 days delinquent, still on accrual	23,833,000	8,995,000
Net loans held for investment	79,469,000	101,444,000
Loans held for sale on nonaccrual status	0	4,529,000
Nonperforming [Member] | Commercial and agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment on nonaccrual status	2,746,000	4,636,000
Loans more than 90 days delinquent, still on accrual	1,103,000	579,000
Nonperforming [Member] | Real estate - construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment on nonaccrual status	14,297,000	30,844,000
Loans more than 90 days delinquent, still on accrual	655,000	302,000
Loans held for sale on nonaccrual status	0	1,807,000
Nonperforming [Member] | Real estate - mortgage, 1-4 family residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment on nonaccrual status	18,372,000	26,048,000
Loans more than 90 days delinquent, still on accrual	4,678,000	1,801,000
Loans held for sale on nonaccrual status	0	517,000
Nonperforming [Member] | Real estate - mortgage, commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment on nonaccrual status	43,621,000	36,666,000
Loans more than 90 days delinquent, still on accrual	17,384,000	6,313,000
Loans held for sale on nonaccrual status	0	2,205,000
Nonperforming [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment on nonaccrual status	206,000	250,000
Loans more than 90 days delinquent, still on accrual	13,000
Loans held for sale on nonaccrual status	0	0
Performing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment on nonaccrual status	79,242,000	98,444,000
Loans more than 90 days delinquent, still on accrual	227,000	3,000,000
Performing [Member] | Commercial and agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment on nonaccrual status	2,746,000	4,636,000
Loans more than 90 days delinquent, still on accrual	50,000	305,000
Performing [Member] | Real estate - construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment on nonaccrual status	14,297,000	30,844,000
Loans more than 90 days delinquent, still on accrual		1,400,000
Performing [Member] | Real estate - mortgage, 1-4 family residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment on nonaccrual status	18,372,000	26,048,000
Loans more than 90 days delinquent, still on accrual		292,000
Performing [Member] | Real estate - mortgage, commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment on nonaccrual status	43,621,000	36,666,000
Loans more than 90 days delinquent, still on accrual	177,000	1,003,000
Performing [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment on nonaccrual status	$ 206,000	$ 250,000