Impaired Loans and Valuation Allowance for Loan Losses (Details 4) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Activity in allowance for loan losses
Allowance, Beginning Balance	$ 22,104	$ 25,565
Provision for Loan Losses	953	2,305
Charge-offs	(1,896)	(3,681)
Recoveries	379	266
Net Charge-offs	(1,517)	(3,415)
Allowance, Ending Balance	21,540	24,455
Construction and land development [Member]
Activity in allowance for loan losses
Allowance, Beginning Balance	1,134	1,883
Provision for Loan Losses	193	(159)
Charge-offs	(334)	(230)
Recoveries	115	15
Net Charge-offs	(219)	(215)
Allowance, Ending Balance	1,108	1,509
Commercial real estate [Member]
Activity in allowance for loan losses
Allowance, Beginning Balance	8,849	11,477
Provision for Loan Losses	49	1,645
Charge-offs	(529)	(2,287)
Recoveries	79	76
Net Charge-offs	(450)	(2,211)
Allowance, Ending Balance	8,448	10,911
Residential real estate [Member]
Activity in allowance for loan losses
Allowance, Beginning Balance	11,090	10,966
Provision for Loan Losses	481	864
Charge-offs	(946)	(1,054)
Recoveries	97	50
Net Charge-offs	(849)	(1,004)
Allowance, Ending Balance	10,722	10,826
Commercial and financial [Member]
Activity in allowance for loan losses
Allowance, Beginning Balance	468	402
Provision for Loan Losses	70	78
Charge-offs	(60)	(97)
Recoveries	80	34
Net Charge-offs	20	(63)
Allowance, Ending Balance	558	417
Consumer [Member]
Activity in allowance for loan losses
Allowance, Beginning Balance	563	837
Provision for Loan Losses	160	(123)
Charge-offs	(27)	(13)
Recoveries	8	91
Net Charge-offs	(19)	78
Allowance, Ending Balance	$ 704	$ 792