Impaired Loans and Valuation Allowance for Loan Losses (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Company's average recorded investments in impaired loans and related interest income
Average Recorded Investment, Total	$ 80,727	$ 99,894
Interest Income Recognized, Total	480	669
Construction and land development [Member]
Company's average recorded investments in impaired loans and related interest income
With No Related Allowance, Average Recorded Investment	1,675	1,601
With Related Allowance, Average Recorded Investment	2,196	3,801
Average Recorded Investment, Total	3,871	5,402
With No Related Allowance, Interest Income Recognized	25	1
With Related Allowance, Interest Income Recognized	6	31
Interest Income Recognized, Total	31	32
Commercial real estate [Member]
Company's average recorded investments in impaired loans and related interest income
With No Related Allowance, Average Recorded Investment	10,806	15,474
With Related Allowance, Average Recorded Investment	26,154	41,663
Average Recorded Investment, Total	36,960	57,137
With No Related Allowance, Interest Income Recognized	2	13
With Related Allowance, Interest Income Recognized	299	399
Interest Income Recognized, Total	301	412
Residential real estate [Member]
Company's average recorded investments in impaired loans and related interest income
With No Related Allowance, Average Recorded Investment	15,338	9,073
With Related Allowance, Average Recorded Investment	23,854	27,106
Average Recorded Investment, Total	39,192	36,179
With No Related Allowance, Interest Income Recognized	2	2
With Related Allowance, Interest Income Recognized	140	216
Interest Income Recognized, Total	142	218
Commercial and financial [Member]
Company's average recorded investments in impaired loans and related interest income
With No Related Allowance, Average Recorded Investment	0	14
With Related Allowance, Average Recorded Investment	0	67
Average Recorded Investment, Total	0	81
With No Related Allowance, Interest Income Recognized	0	0
With Related Allowance, Interest Income Recognized	0	0
Interest Income Recognized, Total	0	0
Consumer [Member]
Company's average recorded investments in impaired loans and related interest income
With No Related Allowance, Average Recorded Investment	178	490
With Related Allowance, Average Recorded Investment	526	605
Average Recorded Investment, Total	704	1,095
With No Related Allowance, Interest Income Recognized	0	0
With Related Allowance, Interest Income Recognized	6	7
Interest Income Recognized, Total	$ 6	$ 7