Impaired Loans and Valuation Allowance for Loan Losses (Details 4) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Transactions in allowance for loan losses
Allowance, Beginning Balance	$ 24,455	$ 34,353	$ 25,565	$ 37,744
Provision for Loan Losses	6,455	902	8,760	1,542
Charge-offs	(6,698)	(4,177)	(10,379)	(8,713)
Recoveries	423	153	689	658
Net Charge-offs	(6,275)	(4,024)	(9,690)	(8,055)
Allowance, Ending Balance	24,635	31,231	24,635	31,231
Construction and land development [Member]
Transactions in allowance for loan losses
Allowance, Beginning Balance	1,509	4,112	1,883	7,214
Provision for Loan Losses	24	(244)	(135)	(1,802)
Charge-offs	(249)	(1,848)	(479)	(3,698)
Recoveries	71	11	86	317
Net Charge-offs	(178)	(1,837)	(393)	(3,381)
Allowance, Ending Balance	1,355	2,031	1,355	2,031
Commercial real estate [Member]
Transactions in allowance for loan losses
Allowance, Beginning Balance	10,911	16,767	11,477	18,563
Provision for Loan Losses	4,415	153	6,060	(1,073)
Charge-offs	(3,444)	(676)	(5,731)	(1,257)
Recoveries	95	7	171	18
Net Charge-offs	(3,349)	(669)	(5,560)	(1,239)
Allowance, Ending Balance	11,977	16,251	11,977	16,251
Residential real estate [Member]
Transactions in allowance for loan losses
Allowance, Beginning Balance	10,826	11,530	10,966	10,102
Provision for Loan Losses	2,042	1,403	2,906	4,678
Charge-offs	(2,770)	(1,631)	(3,824)	(3,554)
Recoveries	214	73	264	149
Net Charge-offs	(2,556)	(1,558)	(3,560)	(3,405)
Allowance, Ending Balance	10,312	11,375	10,312	11,375
Commercial and financial [Member]
Transactions in allowance for loan losses
Allowance, Beginning Balance	417	739	402	480
Provision for Loan Losses	72	(212)	150	(40)
Charge-offs	(194)	0	(291)	0
Recoveries	34	45	68	132
Net Charge-offs	(160)	45	(223)	132
Allowance, Ending Balance	329	572	329	572
Consumer [Member]
Transactions in allowance for loan losses
Allowance, Beginning Balance	792	1,205	837	1,385
Provision for Loan Losses	(98)	(198)	(221)	(221)
Charge-offs	(41)	(22)	(54)	(204)
Recoveries	9	17	100	42
Net Charge-offs	(32)	(5)	46	(162)
Allowance, Ending Balance	$ 662	$ 1,002	$ 662	$ 1,002