Impaired Loans and Valuation Allowance for Loan Losses (Details 4) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Transactions in allowance for loan losses
Allowance, Beginning Balance	$ 24,635	$ 31,231	$ 25,565	$ 37,744
Provision for Loan Losses	900	0	9,660	1,542
Charge-offs	(3,027)	(3,375)	(13,406)	(12,088)
Recoveries	611	545	1,300	1,203
Net Charge-offs	(2,416)	(2,830)	(12,106)	(10,885)
Allowance, Ending Balance	23,119	28,401	23,119	28,401
Construction and Land Development [Member]
Transactions in allowance for loan losses
Allowance, Beginning Balance	1,355	2,031	1,883	7,214
Provision for Loan Losses	(194)	331	(329)	(1,471)
Charge-offs	(92)	(720)	(571)	(4,418)
Recoveries	210	190	296	507
Net Charge-offs	118	(530)	(275)	(3,911)
Allowance, Ending Balance	1,279	1,832	1,279	1,832
Commercial Real Estate [Member]
Transactions in allowance for loan losses
Allowance, Beginning Balance	11,977	16,251	11,477	18,563
Provision for Loan Losses	225	(2,686)	6,285	(3,759)
Charge-offs	(1,906)	(74)	(7,637)	(1,331)
Recoveries	117	16	288	34
Net Charge-offs	(1,789)	(58)	(7,349)	(1,297)
Allowance, Ending Balance	10,413	13,507	10,413	13,507
Residential Real Estate [Member]
Transactions in allowance for loan losses
Allowance, Beginning Balance	10,312	11,375	10,966	10,102
Provision for Loan Losses	950	2,527	3,856	7,205
Charge-offs	(995)	(2,368)	(4,819)	(5,922)
Recoveries	234	196	498	345
Net Charge-offs	(761)	(2,172)	(4,321)	(5,577)
Allowance, Ending Balance	10,501	11,730	10,501	11,730
Commercial and Financial [Member]
Transactions in allowance for loan losses
Allowance, Beginning Balance	329	572	402	480
Provision for Loan Losses	(34)	(309)	116	(349)
Charge-offs	0	0	(291)	0
Recoveries	40	131	108	263
Net Charge-offs	40	131	(183)	263
Allowance, Ending Balance	335	394	335	394
Consumer [Member]
Transactions in allowance for loan losses
Allowance, Beginning Balance	662	1,002	837	1,385
Provision for Loan Losses	(47)	137	(268)	(84)
Charge-offs	(34)	(213)	(88)	(417)
Recoveries	10	12	110	54
Net Charge-offs	(24)	(201)	22	(363)
Allowance, Ending Balance	$ 591	$ 938	$ 591	$ 938