Impaired Loans and Valuation Allowance for Loan Losses (Details 3) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Company's average recorded investments in impaired loans and related interest income
Average Recorded Investment, Total	$ 76,302	$ 100,304
Interest Income Recognized, Total	669	1,709
Construction and land development [Member]
Company's average recorded investments in impaired loans and related interest income
With No Related Allowance, Average Recorded Investment	2,216	1,569
With Related Allowance, Average Recorded Investment	1,547	3,750
Average Recorded Investment, Total	3,763	5,319
With No Related Allowance, Interest Income Recognized	50	2
With Related Allowance, Interest Income Recognized	19	64
Interest Income Recognized, Total	69	66
Commercial real estate [Member]
Company's average recorded investments in impaired loans and related interest income
With No Related Allowance, Average Recorded Investment	9,194	12,167
With Related Allowance, Average Recorded Investment	24,115	43,870
Average Recorded Investment, Total	33,309	56,037
With No Related Allowance, Interest Income Recognized	18	155
With Related Allowance, Interest Income Recognized	274	902
Interest Income Recognized, Total	292	1,057
Residential real estate [Member]
Company's average recorded investments in impaired loans and related interest income
With No Related Allowance, Average Recorded Investment	15,084	10,145
With Related Allowance, Average Recorded Investment	23,418	27,648
Average Recorded Investment, Total	38,502	37,793
With No Related Allowance, Interest Income Recognized	10	137
With Related Allowance, Interest Income Recognized	286	429
Interest Income Recognized, Total	296	566
Commercial and financial [Member]
Company's average recorded investments in impaired loans and related interest income
With No Related Allowance, Average Recorded Investment	0	11
With Related Allowance, Average Recorded Investment	0	39
Average Recorded Investment, Total	0	50
With No Related Allowance, Interest Income Recognized	0	0
With Related Allowance, Interest Income Recognized	0	8
Interest Income Recognized, Total	0	8
Consumer [Member]
Company's average recorded investments in impaired loans and related interest income
With No Related Allowance, Average Recorded Investment	142	486
With Related Allowance, Average Recorded Investment	586	619
Average Recorded Investment, Total	728	1,105
With No Related Allowance, Interest Income Recognized	1	1
With Related Allowance, Interest Income Recognized	11	11
Interest Income Recognized, Total	$ 12	$ 12