Impaired Loans and Valuation Allowance for Loan Losses (Details 4) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Activity in allowance for loan losses
Allowance, Beginning Balance	$ 21,540	$ 24,455	$ 22,104	$ 25,565
Provision for Loan Losses	565	6,455	1,518	8,760
Charge-Offs	(2,618)	(6,698)	(4,514)	(10,379)
Recoveries	591	423	970	689
Net Charge-Offs	(2,027)	(6,275)	(3,544)	(9,690)
Allowance, Ending Balance	20,078	24,635	20,078	24,635
Construction and land development [Member]
Activity in allowance for loan losses
Allowance, Beginning Balance	1,108	1,509	1,134	1,883
Provision for Loan Losses	(26)	24	167	(135)
Charge-Offs	(223)	(249)	(557)	(479)
Recoveries	18	71	133	86
Net Charge-Offs	(205)	(178)	(424)	(393)
Allowance, Ending Balance	877	1,355	877	1,355
Commercial real estate [Member]
Activity in allowance for loan losses
Allowance, Beginning Balance	8,448	10,911	8,849	11,477
Provision for Loan Losses	(427)	4,415	(378)	6,060
Charge-Offs	(1,517)	(3,444)	(2,046)	(5,731)
Recoveries	221	95	300	171
Net Charge-Offs	(1,296)	(3,349)	(1,746)	(5,560)
Allowance, Ending Balance	6,725	11,977	6,725	11,977
Residential real estate [Member]
Activity in allowance for loan losses
Allowance, Beginning Balance	10,722	10,826	11,090	10,966
Provision for Loan Losses	1,107	2,042	1,588	2,906
Charge-Offs	(826)	(2,770)	(1,772)	(3,824)
Recoveries	150	214	247	264
Net Charge-Offs	(676)	(2,556)	(1,525)	(3,560)
Allowance, Ending Balance	11,153	10,312	11,153	10,312
Commercial and financial [Member]
Activity in allowance for loan losses
Allowance, Beginning Balance	558	417	468	402
Provision for Loan Losses	(193)	72	(123)	150
Charge-Offs	0	(194)	(60)	(291)
Recoveries	198	34	278	68
Net Charge-Offs	198	(160)	218	(223)
Allowance, Ending Balance	563	329	563	329
Consumer [Member]
Activity in allowance for loan losses
Allowance, Beginning Balance	704	792	563	837
Provision for Loan Losses	104	(98)	264	(221)
Charge-Offs	(52)	(41)	(79)	(54)
Recoveries	4	9	12	100
Net Charge-Offs	(48)	(32)	(67)	46
Allowance, Ending Balance	$ 760	$ 662	$ 760	$ 662