Loans - Schedule of Recorded Investment in Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	$ 114,329		$ 114,329		$ 132,785
Recorded Investment With No Allowance	49,502		49,502		57,992
Recorded Investment With Allowance	40,946		40,946		46,699
Total Recorded Investment	90,448		90,448		104,691
Related Allowance	13,903		13,903		13,954
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	93,841	$ 81,974	97,573	$ 82,798
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	108	192	506	414
Interest Income on Impaired Loans If Interest Had Been Accrued	946	993	1,814	2,994
Commercial
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	47,934		47,934		57,017
Recorded Investment With No Allowance	21,558		21,558		24,410
Recorded Investment With Allowance	16,035		16,035		21,420
Total Recorded Investment	37,593		37,593		45,830
Related Allowance	3,947		3,947		2,847
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	40,362	33,408	41,712	35,572
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	54	100	281	241
Land acquisition & development
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	11,290		11,290		12,084
Recorded Investment With No Allowance	3,694		3,694		4,330
Recorded Investment With Allowance	1,714		1,714		1,813
Total Recorded Investment	5,408		5,408		6,143
Related Allowance	711		711		826
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	5,383	6,797	5,776	6,992
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	2	13	10	32
Residential
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	310		310		1,555
Recorded Investment With No Allowance	205		205		219
Recorded Investment With Allowance	0		0		619
Total Recorded Investment	205		205		838
Related Allowance	0		0		1
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	207	274	522	279
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	4,725		4,725		4,786
Recorded Investment With No Allowance	417		417		3,940
Recorded Investment With Allowance	3,537		3,537		647
Total Recorded Investment	3,954		3,954		4,587
Related Allowance	2,148		2,148		657
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	4,192	1,055	4,271	1,007
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	1	1	45	3
Total construction loans
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	16,325		16,325		18,425
Recorded Investment With No Allowance	4,316		4,316		8,489
Recorded Investment With Allowance	5,251		5,251		3,079
Total Recorded Investment	9,567		9,567		11,568
Related Allowance	2,859		2,859		1,484
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	9,782	8,126	10,569	8,278
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	3	14	55	35
Residential
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	8,990		8,990		8,222
Recorded Investment With No Allowance	5,629		5,629		4,074
Recorded Investment With Allowance	2,122		2,122		2,470
Total Recorded Investment	7,751		7,751		6,544
Related Allowance	218		218		253
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	7,123	3,282	7,148	4,219
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	4	4	12	7
Agricultural
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	2,681		2,681		5,069
Recorded Investment With No Allowance	2,425		2,425		4,509
Recorded Investment With Allowance	156		156		181
Total Recorded Investment	2,581		2,581		4,690
Related Allowance	4		4		4
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	2,642	4,786	3,636	4,607
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	0	2	0	3
Total real estate loans
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	75,930		75,930		88,733
Recorded Investment With No Allowance	33,928		33,928		41,482
Recorded Investment With Allowance	23,564		23,564		27,150
Total Recorded Investment	57,492		57,492		68,632
Related Allowance	7,028		7,028		4,588
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	59,909	49,602	63,065	52,676
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	61	120	348	286
Total consumer loans
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	27		27
Recorded Investment With No Allowance	0		0
Recorded Investment With Allowance	25		25
Total Recorded Investment	25		25
Related Allowance	14		14
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	25	0	13	0
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	0		0	0
Commercial
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	36,787		36,787		40,314
Recorded Investment With No Allowance	14,623		14,623		13,230
Recorded Investment With Allowance	16,748		16,748		19,167
Total Recorded Investment	31,371		31,371		32,397
Related Allowance	6,426		6,426		9,254
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	31,637	30,123	31,884	27,781
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	47	72	156	128
Agricultural
Impaired Financing Receivable, Unpaid Principal Balance
Unpaid Total Principal Balance	1,585		1,585		3,738
Recorded Investment With No Allowance	951		951		3,280
Recorded Investment With Allowance	609		609		382
Total Recorded Investment	1,560		1,560		3,662
Related Allowance	435		435		$ 112
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income
Average Recorded Investment	2,270	2,249	2,611	2,341
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Income Recognized	$ 0	$ 0	$ 2	$ 0