Allowance for Credit Losses, Allocation of The Allowance For Loan Losses by Portfolio Segment and By Impairment Methodology (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for Credit Losses [Roll Forward]
Beginning Balance				$ 55,266				$ 50,342	$ 55,266	$ 50,342
Charge-Offs									(675)	(767)
Recoveries									221	158
Provision	$ 0	$ 0	$ 200	0	$ 2,200	$ 2,500	$ 500	333	200	5,533	$ 2,850
Ending Balance	55,012				55,266				55,012	55,266	50,342
Ending Balance Individually Evaluated for Impairment	661				565				661	565
Ending Balance Collectively Evaluated for Impairment	54,351				54,701				54,351	54,701
Loans & Leases [Abstract]
Ending Balance	2,673,027				2,571,241				2,673,027	2,571,241
Ending Balance Individually Evaluated for Impairment	14,691				16,347				14,691	16,347
Ending Balance Collectively Evaluated for Impairment	2,658,336				2,554,894				2,658,336	2,554,894
Commercial Real Estate [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				11,609				10,922	11,609	10,922
Charge-Offs									0	0
Recoveries									0	2
Provision									(556)	685
Ending Balance	11,053				11,609				11,053	11,609	10,922
Ending Balance Individually Evaluated for Impairment	234				234				234	234
Ending Balance Collectively Evaluated for Impairment	10,819				11,375				10,819	11,375
Loans & Leases [Abstract]
Ending Balance	838,570				826,549				838,570	826,549
Ending Balance Individually Evaluated for Impairment	4,524				4,676				4,524	4,676
Ending Balance Collectively Evaluated for Impairment	834,046				821,873				834,046	821,873
Agricultural Real Estate [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				14,092				12,085	14,092	12,085
Charge-Offs									0	0
Recoveries									38	0
Provision									998	2,007
Ending Balance	15,128				14,092				15,128	14,092	12,085
Ending Balance Individually Evaluated for Impairment	0				0				0	0
Ending Balance Collectively Evaluated for Impairment	15,128				14,092				15,128	14,092
Loans & Leases [Abstract]
Ending Balance	625,767				584,625				625,767	584,625
Ending Balance Individually Evaluated for Impairment	5,654				7,238				5,654	7,238
Ending Balance Collectively Evaluated for Impairment	620,113				577,387				620,113	577,387
Real Estate Construction [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				1,249				1,846	1,249	1,846
Charge-Offs									0	0
Recoveries									0	0
Provision									700	(597)
Ending Balance	1,949				1,249				1,949	1,249	1,846
Ending Balance Individually Evaluated for Impairment	0				0				0	0
Ending Balance Collectively Evaluated for Impairment	1,949				1,249				1,949	1,249
Loans & Leases [Abstract]
Ending Balance	115,644				98,568				115,644	98,568
Ending Balance Individually Evaluated for Impairment	0				0				0	0
Ending Balance Collectively Evaluated for Impairment	115,644				98,568				115,644	98,568
Residential 1st Mortgages [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				880				815	880	815
Charge-Offs									0	(31)
Recoveries									13	15
Provision									(38)	81
Ending Balance	855				880				855	880	815
Ending Balance Individually Evaluated for Impairment	118				125				118	125
Ending Balance Collectively Evaluated for Impairment	737				755				737	755
Loans & Leases [Abstract]
Ending Balance	255,253				259,736				255,253	259,736
Ending Balance Individually Evaluated for Impairment	2,368				2,491				2,368	2,491
Ending Balance Collectively Evaluated for Impairment	252,885				257,245				252,885	257,245
Home Equity Lines and Loans [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				2,761				2,324	2,761	2,324
Charge-Offs									0	(8)
Recoveries									28	6
Provision									(114)	439
Ending Balance	2,675				2,761				2,675	2,761	2,324
Ending Balance Individually Evaluated for Impairment	12				15				12	15
Ending Balance Collectively Evaluated for Impairment	2,663				2,746				2,663	2,746
Loans & Leases [Abstract]
Ending Balance	39,270				40,789				39,270	40,789
Ending Balance Individually Evaluated for Impairment	229				297				229	297
Ending Balance Collectively Evaluated for Impairment	39,041				40,492				39,041	40,492
Agricultural [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				8,242				8,159	8,242	8,159
Charge-Offs									0	0
Recoveries									0	61
Provision									(166)	22
Ending Balance	8,076				8,242				8,076	8,242	8,159
Ending Balance Individually Evaluated for Impairment	99				0				99	0
Ending Balance Collectively Evaluated for Impairment	7,977				8,242				7,977	8,242
Loans & Leases [Abstract]
Ending Balance	292,904				290,463				292,904	290,463
Ending Balance Individually Evaluated for Impairment	188				0				188	0
Ending Balance Collectively Evaluated for Impairment	292,716				290,463				292,716	290,463
Commercial [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				11,656				9,197	11,656	9,197
Charge-Offs									(592)	(613)
Recoveries									90	20
Provision									312	3,052
Ending Balance	11,466				11,656				11,466	11,656	9,197
Ending Balance Individually Evaluated for Impairment	137				185				137	185
Ending Balance Collectively Evaluated for Impairment	11,329				11,471				11,329	11,471
Loans & Leases [Abstract]
Ending Balance	384,795				343,834				384,795	343,834
Ending Balance Individually Evaluated for Impairment	1,528				1,639				1,528	1,639
Ending Balance Collectively Evaluated for Impairment	383,267				342,195				383,267	342,195
Consumer & Other [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				494				209	494	209
Charge-Offs									(83)	(115)
Recoveries									52	54
Provision									(7)	346
Ending Balance	456				494				456	494	209
Ending Balance Individually Evaluated for Impairment	61				6				61	6
Ending Balance Collectively Evaluated for Impairment	395				488				395	488
Loans & Leases [Abstract]
Ending Balance	15,422				19,412				15,422	19,412
Ending Balance Individually Evaluated for Impairment	200				6				200	6
Ending Balance Collectively Evaluated for Impairment	15,222				19,406				15,222	19,406
Leases [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				4,022				3,363	4,022	3,363
Charge-Offs									0	0
Recoveries									0	0
Provision									(860)	659
Ending Balance	3,162				4,022				3,162	4,022	3,363
Ending Balance Individually Evaluated for Impairment	0				0				0	0
Ending Balance Collectively Evaluated for Impairment	3,162				4,022				3,162	4,022
Loans & Leases [Abstract]
Ending Balance	105,402				107,265				105,402	107,265
Ending Balance Individually Evaluated for Impairment	0				0				0	0
Ending Balance Collectively Evaluated for Impairment	105,402				107,265				105,402	107,265
Unallocated [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				$ 261				$ 1,422	261	1,422
Charge-Offs									0	0
Recoveries									0	0
Provision									(69)	(1,161)
Ending Balance	192				261				192	261	$ 1,422
Ending Balance Individually Evaluated for Impairment	0				0				0	0
Ending Balance Collectively Evaluated for Impairment	192				261				192	261
Loans & Leases [Abstract]
Ending Balance	0				0				0	0
Ending Balance Individually Evaluated for Impairment	0				0				0	0
Ending Balance Collectively Evaluated for Impairment	0				0				0	0
Restructured Loans [Member]
Loans & Leases [Abstract]
Ending Balance Individually Evaluated for Impairment	$ 2,600				$ 2,800				$ 2,600	$ 2,800