Loans Schedule of Recorded Investment in Impaired Loans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	$ 123,673		$ 123,673		$ 158,512
Recorded Investment With No Allowance	66,740		66,740		82,232
Recorded Investment With Allowance	44,836		44,836		53,953
Total Recorded Investment	111,576		111,576		136,185
Related Allowance	13,361		13,361		10,297
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	116,759	165,816	124,792	198,334
Income Recognized	286	431	1,413	1,260
Interest Income on Impaired Loans If Interest Had Been Accrued	1,481	2,276	4,832	8,249
Commercial real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	62,453		62,453		84,300
Recorded Investment With No Allowance	33,566		33,566		39,049
Recorded Investment With Allowance	26,993		26,993		34,774
Total Recorded Investment	60,559		60,559		73,823
Related Allowance	4,897		4,897		4,112
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	62,208	81,313	65,726	82,689
Income Recognized	239	366	849	1,037
Land acquisition & development construction real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	22,985		22,985		28,558
Recorded Investment With No Allowance	11,211		11,211		15,891
Recorded Investment With Allowance	7,327		7,327		7,173
Total Recorded Investment	18,538		18,538		23,064
Related Allowance	2,652		2,652		1,457
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	17,614	36,206	19,923	49,528
Income Recognized	19	30	475	76
Residential construction real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	2,191		2,191		3,018
Recorded Investment With No Allowance	1,490		1,490		1,976
Recorded Investment With Allowance	0		0		710
Total Recorded Investment	1,490		1,490		2,686
Related Allowance	0		0		251
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	1,513	3,151	1,949	8,591
Income Recognized	0	0	0	0
Commercial construction real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	442		442		10,447
Recorded Investment With No Allowance	360		360		7,785
Recorded Investment With Allowance	48		48		340
Total Recorded Investment	408		408		8,125
Related Allowance	48		48		69
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	1,174	10,817	5,161	18,601
Income Recognized	2	0	2	0
Total construction loans
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	25,618		25,618		42,023
Recorded Investment With No Allowance	13,061		13,061		25,652
Recorded Investment With Allowance	7,375		7,375		8,223
Total Recorded Investment	20,436		20,436		33,875
Related Allowance	2,700		2,700		1,777
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	20,301	50,174	27,033	76,720
Income Recognized	21	30	477	76
Residential real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	9,682		9,682		13,271
Recorded Investment With No Allowance	4,869		4,869		6,152
Recorded Investment With Allowance	1,840		1,840		4,495
Total Recorded Investment	6,709		6,709		10,647
Related Allowance	657		657		1,677
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	7,770	12,416	8,882	14,667
Income Recognized	6	1	15	22
Agricultural real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	10,108		10,108		5,559
Recorded Investment With No Allowance	6,724		6,724		1,834
Recorded Investment With Allowance	3,289		3,289		3,227
Total Recorded Investment	10,013		10,013		5,061
Related Allowance	962		962		784
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	9,995	5,173	7,751	7,090
Income Recognized	0	9	8	41
Total real estate loans
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	107,861		107,861		145,153
Recorded Investment With No Allowance	58,220		58,220		72,687
Recorded Investment With Allowance	39,497		39,497		50,719
Total Recorded Investment	97,717		97,717		123,406
Related Allowance	9,216		9,216		8,350
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	100,274	149,076	109,392	181,166
Income Recognized	266	406	1,349	1,176
Commercial
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	15,645		15,645		12,770
Recorded Investment With No Allowance	8,493		8,493		9,036
Recorded Investment With Allowance	5,250		5,250		3,206
Total Recorded Investment	13,743		13,743		12,242
Related Allowance	4,126		4,126		1,919
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	16,245	15,992	15,065	16,129
Income Recognized	16	21	52	65
Agricultural
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	167		167		589
Recorded Investment With No Allowance	27		27		509
Recorded Investment With Allowance	89		89		28
Total Recorded Investment	116		116		537
Related Allowance	19		19		28
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	240	748	335	1,039
Income Recognized	$ 4	$ 4	$ 12	$ 19