Loans Schedule of Recorded Investment in Impaired Loans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	$ 136,650		$ 136,650		$ 158,512
Recorded Investment With No Allowance	67,570		67,570		82,232
Recorded Investment With Allowance	56,520		56,520		53,953
Total Recorded Investment	124,090		124,090		136,185
Related Allowance	15,494		15,494		10,297
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	127,553	200,803	127,499	217,702
Income Recognized	318	395	1,127	829
Interest Income on Impaired Loans If Interest Had Been Accrued	406	580
Commercial real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	65,957		65,957		84,300
Recorded Investment With No Allowance	32,854		32,854		39,049
Recorded Investment With Allowance	31,688		31,688		34,774
Total Recorded Investment	64,542		64,542		73,823
Related Allowance	5,498		5,498		4,112
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	67,605	87,135	67,192	85,701
Income Recognized	272	320	610	671
Land acquisition & development construction real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	21,554		21,554		28,558
Recorded Investment With No Allowance	10,526		10,526		15,891
Recorded Investment With Allowance	6,755		6,755		7,173
Total Recorded Investment	17,281		17,281		23,064
Related Allowance	2,549		2,549		1,457
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	19,007	51,949	20,123	56,924
Income Recognized	15	30	456	46
Residential construction real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	2,227		2,227		3,018
Recorded Investment With No Allowance	1,526		1,526		1,976
Recorded Investment With Allowance	0		0		710
Total Recorded Investment	1,526		1,526		2,686
Related Allowance	0		0		251
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	1,569	3,637	2,040	8,810
Income Recognized	0	0	0	0
Commercial construction real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	8,374		8,374		10,447
Recorded Investment With No Allowance	5,944		5,944		7,785
Recorded Investment With Allowance	248		248		340
Total Recorded Investment	6,192		6,192		8,125
Related Allowance	63		63		69
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	6,346	20,807	7,118	22,536
Income Recognized	0	0	0	0
Total construction loans
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	32,155		32,155		42,023
Recorded Investment With No Allowance	17,996		17,996		25,652
Recorded Investment With Allowance	7,003		7,003		8,223
Total Recorded Investment	24,999		24,999		33,875
Related Allowance	2,612		2,612		1,777
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	26,922	76,393	29,281	88,270
Income Recognized	15	30	456	46
Residential real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	10,554		10,554		13,271
Recorded Investment With No Allowance	2,448		2,448		6,152
Recorded Investment With Allowance	5,331		5,331		4,495
Total Recorded Investment	7,779		7,779		10,647
Related Allowance	1,253		1,253		1,677
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	8,311	14,726	9,429	16,251
Income Recognized	5	12	9	21
Agricultural real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	10,017		10,017		5,559
Recorded Investment With No Allowance	7,363		7,363		1,834
Recorded Investment With Allowance	2,558		2,558		3,227
Total Recorded Investment	9,921		9,921		5,061
Related Allowance	904		904		784
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	8,255	6,816	6,611	10,039
Income Recognized	4	0	8	32
Total real estate loans
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	118,683		118,683		145,153
Recorded Investment With No Allowance	60,661		60,661		72,687
Recorded Investment With Allowance	46,580		46,580		50,719
Total Recorded Investment	107,241		107,241		123,406
Related Allowance	10,267		10,267		8,350
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	111,093	185,070	112,513	200,261
Income Recognized	296	362	1,083	770
Commercial
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	17,776		17,776		12,770
Recorded Investment With No Allowance	6,792		6,792		9,036
Recorded Investment With Allowance	9,918		9,918		3,206
Total Recorded Investment	16,710		16,710		12,242
Related Allowance	5,205		5,205		1,919
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	16,087	14,355	14,484	16,195
Income Recognized	18	22	36	44
Agricultural
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	191		191		589
Recorded Investment With No Allowance	117		117		509
Recorded Investment With Allowance	22		22		28
Total Recorded Investment	139		139		537
Related Allowance	22		22		28
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	373	1,378	502	1,246
Income Recognized	$ 4	$ 11	$ 8	$ 15