Loans Schedule of Recorded Investment in Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	$ 122,901		$ 122,901		$ 132,785
Recorded Investment With No Allowance	48,907		48,907		57,992
Recorded Investment With Allowance	48,324		48,324		46,699
Total Recorded Investment	97,231		97,231		104,691
Related Allowance	16,316		16,316		13,954
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	97,492	$ 81,121	100,963	$ 84,122
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	171	162	398	222
Interest Income on Impaired Loans If Interest Had Been Accrued	919	964	1,772	2,020
Commercial real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	53,576		53,576		57,017
Recorded Investment With No Allowance	22,751		22,751		24,410
Recorded Investment With Allowance	20,380		20,380		21,420
Total Recorded Investment	43,131		43,131		45,830
Related Allowance	5,158		5,158		2,847
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	43,871	34,576	44,481	36,342
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	102	105	227	141
Land acquisition & development construction real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	11,281		11,281		12,084
Recorded Investment With No Allowance	3,639		3,639		4,330
Recorded Investment With Allowance	1,718		1,718		1,813
Total Recorded Investment	5,357		5,357		6,143
Related Allowance	741		741		826
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	5,411	7,096	5,750	7,277
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	4	12	8	19
Residential construction real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	312		312		1,555
Recorded Investment With No Allowance	209		209		219
Recorded Investment With Allowance	0		0		619
Total Recorded Investment	209		209		838
Related Allowance	0		0		1
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	212	277	524	282
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	0	0	0	0
Commercial construction real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	4,728		4,728		4,786
Recorded Investment With No Allowance	226		226		3,940
Recorded Investment With Allowance	4,204		4,204		647
Total Recorded Investment	4,430		4,430		4,587
Related Allowance	2,828		2,828		657
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	4,463	1,421	4,509	1,433
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	1	2	44	2
Total construction loans
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	16,321		16,321		18,425
Recorded Investment With No Allowance	4,074		4,074		8,489
Recorded Investment With Allowance	5,922		5,922		3,079
Total Recorded Investment	9,996		9,996		11,568
Related Allowance	3,569		3,569		1,484
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	10,086	8,794	10,783	8,992
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	5	14	52	21
Residential real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	7,636		7,636		8,222
Recorded Investment With No Allowance	4,472		4,472		4,074
Recorded Investment With Allowance	2,022		2,022		2,470
Total Recorded Investment	6,494		6,494		6,544
Related Allowance	170		170		253
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	6,574	3,067	6,519	4,138
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	4	2	8	3
Agricultural real estate
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	2,752		2,752		5,069
Recorded Investment With No Allowance	2,549		2,549		4,509
Recorded Investment With Allowance	153		153		181
Total Recorded Investment	2,702		2,702		4,690
Related Allowance	9		9		4
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	2,389	5,857	3,696	5,671
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	0	0	0	1
Total real estate loans
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	80,285		80,285		88,733
Recorded Investment With No Allowance	33,846		33,846		41,482
Recorded Investment With Allowance	28,477		28,477		27,150
Total Recorded Investment	62,323		62,323		68,632
Related Allowance	8,906		8,906		4,588
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	62,920	52,294	65,479	55,143
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	111	121	287	166
Total consumer loans
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	28		28
Recorded Investment With No Allowance	0		0
Recorded Investment With Allowance	25		25
Total Recorded Investment	25		25
Related Allowance	0		0
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	13	0	13	0
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	0	0	0	0
Commercial
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	39,587		39,587		40,314
Recorded Investment With No Allowance	13,021		13,021		13,230
Recorded Investment With Allowance	18,882		18,882		19,167
Total Recorded Investment	31,903		31,903		32,397
Related Allowance	6,882		6,882		9,254
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	32,491	28,074	32,150	28,133
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	60	41	109	56
Agricultural
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	3,001		3,001		3,738
Recorded Investment With No Allowance	2,040		2,040		3,280
Recorded Investment With Allowance	940		940		382
Total Recorded Investment	2,980		2,980		3,662
Related Allowance	528		528		$ 112
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	2,068	753	3,321	846
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	$ 0	$ 0	$ 2	$ 0

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5258-111524

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Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953550-111524

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Recorded Investment
-URI http://asc.fasb.org/extlink&oid=65880944

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
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