Loans Schedule of Recorded Investment in Impaired Loans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	$ 153,522		$ 158,512
Recorded Investment With No Allowance	71,581		82,232
Recorded Investment With Allowance	59,092		53,953
Total Recorded Investment	130,673		136,185
Related Allowance	12,117		10,297
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	135,579	228,816
Income Recognized	809	456
Interest Income on Impaired Loans If Interest Had Been Accrued	1,335	2,683
Commercial real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	82,456		84,300
Recorded Investment With No Allowance	34,042		39,049
Recorded Investment With Allowance	38,695		34,774
Total Recorded Investment	72,737		73,823
Related Allowance	4,429		4,112
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	73,936	88,657
Income Recognized	338	188
Land acquisition & development construction real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	25,929		28,558
Recorded Investment With No Allowance	13,976		15,891
Recorded Investment With Allowance	6,560		7,173
Total Recorded Investment	20,536		23,064
Related Allowance	1,703		1,457
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	22,641	62,227
Income Recognized	441	3
Residential construction real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	1,925		3,018
Recorded Investment With No Allowance	1,335		1,976
Recorded Investment With Allowance	0		710
Total Recorded Investment	1,335		2,686
Related Allowance	0		251
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	2,259	9,208
Income Recognized	0	18
Commercial construction real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	9,422		10,447
Recorded Investment With No Allowance	6,227		7,785
Recorded Investment With Allowance	256		340
Total Recorded Investment	6,483		8,125
Related Allowance	68		69
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	7,898	24,265
Income Recognized	0	0
Total construction loans
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	37,276		42,023
Recorded Investment With No Allowance	21,538		25,652
Recorded Investment With Allowance	6,816		8,223
Total Recorded Investment	28,354		33,875
Related Allowance	1,771		1,777
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	32,798	95,700
Income Recognized	441	21
Residential real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	11,649		13,271
Recorded Investment With No Allowance	6,181		6,152
Recorded Investment With Allowance	2,595		4,495
Total Recorded Investment	8,776		10,647
Related Allowance	1,132		1,677
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	10,519	18,072
Income Recognized	4	160
Agricultural real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	5,415		5,559
Recorded Investment With No Allowance	1,724		1,834
Recorded Investment With Allowance	3,098		3,227
Total Recorded Investment	4,822		5,061
Related Allowance	1,035		784
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	4,948	7,268
Income Recognized	4	56
Total real estate loans
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	136,796		145,153
Recorded Investment With No Allowance	63,485		72,687
Recorded Investment With Allowance	51,204		50,719
Total Recorded Investment	114,689		123,406
Related Allowance	8,367		8,350
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	122,201	209,697
Income Recognized	787	425
Commercial
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	16,521		12,770
Recorded Investment With No Allowance	7,969		9,036
Recorded Investment With Allowance	7,863		3,206
Total Recorded Investment	15,832		12,242
Related Allowance	3,725		1,919
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	12,746	17,885
Income Recognized	18	31
Agricultural
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	205		589
Recorded Investment With No Allowance	127		509
Recorded Investment With Allowance	25		28
Total Recorded Investment	152		537
Related Allowance	25		28
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	632	1,234
Income Recognized	$ 4	$ 0