Impaired Loans and Valuation Allowance for Loan Losses (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Company's recorded investments in impaired loans and the related valuation allowances
Recorded Investment, Total	$ 76,378	$ 82,901
Unpaid Principal Balance, Total	87,280	93,023
Related Valuation Allowance, Total	6,713	7,269
Construction and land development [Member]
Company's recorded investments in impaired loans and the related valuation allowances
With No Related Allowance, Recorded Investment	2,768	1,128
With No Related Allowance, Unpaid Principal Balance	3,488	1,608
With No Related Allowance, Related Valuation Allowance	0	0
With Related Allowance, Recorded Investment	793	2,897
With Related Allowance, Unpaid Principal Balance	840	2,941
With Related Allowance, Related Valuation Allowance	183	230
Recorded Investment, Total	3,561	4,025
Unpaid Principal Balance, Total	4,328	4,549
Related Valuation Allowance, Total	183	230
Commercial real estate [Member]
Company's recorded investments in impaired loans and the related valuation allowances
With No Related Allowance, Recorded Investment	7,705	12,357
With No Related Allowance, Unpaid Principal Balance	10,184	14,337
With No Related Allowance, Related Valuation Allowance	0	0
With Related Allowance, Recorded Investment	26,203	26,130
With Related Allowance, Unpaid Principal Balance	26,713	26,648
With Related Allowance, Related Valuation Allowance	1,938	2,264
Recorded Investment, Total	33,908	38,487
Unpaid Principal Balance, Total	36,897	40,985
Related Valuation Allowance, Total	1,938	2,264
Residential real estate [Member]
Company's recorded investments in impaired loans and the related valuation allowances
With No Related Allowance, Recorded Investment	15,088	15,463
With No Related Allowance, Unpaid Principal Balance	21,435	22,022
With No Related Allowance, Related Valuation Allowance	0	0
With Related Allowance, Recorded Investment	23,049	24,256
With Related Allowance, Unpaid Principal Balance	23,798	24,752
With Related Allowance, Related Valuation Allowance	4,410	4,700
Recorded Investment, Total	38,137	39,719
Unpaid Principal Balance, Total	45,233	46,774
Related Valuation Allowance, Total	4,410	4,700
Commercial and financial [Member]
Company's recorded investments in impaired loans and the related valuation allowances
With No Related Allowance, Recorded Investment	0	0
With No Related Allowance, Unpaid Principal Balance	0	0
With No Related Allowance, Related Valuation Allowance	0	0
With Related Allowance, Recorded Investment	0	0
With Related Allowance, Unpaid Principal Balance	0	0
With Related Allowance, Related Valuation Allowance	0	0
Recorded Investment, Total	0	0
Unpaid Principal Balance, Total	0	0
Related Valuation Allowance, Total	0	0
Consumer [Member]
Company's recorded investments in impaired loans and the related valuation allowances
With No Related Allowance, Recorded Investment	89	223
With No Related Allowance, Unpaid Principal Balance	122	255
With No Related Allowance, Related Valuation Allowance	0	0
With Related Allowance, Recorded Investment	683	447
With Related Allowance, Unpaid Principal Balance	700	460
With Related Allowance, Related Valuation Allowance	182	75
Recorded Investment, Total	772	670
Unpaid Principal Balance, Total	822	715
Related Valuation Allowance, Total	$ 182	$ 75