Allowance for Credit Losses, Allocation of The Allowance For Loan Losses by Portfolio Segment and By Impairment Methodology (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for Credit Losses [Roll Forward]
Beginning Balance				$ 55,012,000				$ 55,266,000	$ 55,012,000	$ 55,266,000
Charge-Offs									(1,174,000)	(675,000)
Recoveries									524,000	221,000
Provision	$ 2,500,000	$ 1,700,000	$ 300,000	0	$ 0	$ 0	$ 200,000	0	4,500,000	200,000	$ 5,533,000
Ending Balance	58,862,000				55,012,000				58,862,000	55,012,000	55,266,000
Ending Balance Individually Evaluated for Impairment	289,000				661,000				289,000	661,000
Ending Balance Collectively Evaluated for Impairment	58,573,000				54,351,000				58,573,000	54,351,000
Loans & Leases [Abstract]
Ending Balance	3,099,592,000				2,673,027,000				3,099,592,000	2,673,027,000
Ending Balance Individually Evaluated for Impairment	9,238,000				14,691,000				9,238,000	14,691,000
Ending Balance Collectively Evaluated for Impairment	3,090,354,000				2,658,336,000				3,090,354,000	2,658,336,000
Commercial Real Estate [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				11,053,000				11,609,000	11,053,000	11,609,000
Charge-Offs									0	0
Recoveries									0	0
Provision									16,626,000	(556,000)
Ending Balance	27,679,000				11,053,000				27,679,000	11,053,000	11,609,000
Ending Balance Individually Evaluated for Impairment	0				234,000				0	234,000
Ending Balance Collectively Evaluated for Impairment	27,679,000				10,819,000				27,679,000	10,819,000
Loans & Leases [Abstract]
Ending Balance	958,980,000				838,570,000				958,980,000	838,570,000
Ending Balance Individually Evaluated for Impairment	104,000				4,524,000				104,000	4,524,000
Ending Balance Collectively Evaluated for Impairment	958,876,000				834,046,000				958,876,000	834,046,000
Agricultural Real Estate [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				15,128,000				14,092,000	15,128,000	14,092,000
Charge-Offs									0	0
Recoveries									81,000	38,000
Provision									(6,576,000)	998,000
Ending Balance	8,633,000				15,128,000				8,633,000	15,128,000	14,092,000
Ending Balance Individually Evaluated for Impairment	0				0				0	0
Ending Balance Collectively Evaluated for Impairment	8,633,000				15,128,000				8,633,000	15,128,000
Loans & Leases [Abstract]
Ending Balance	643,014,000				625,767,000				643,014,000	625,767,000
Ending Balance Individually Evaluated for Impairment	5,629,000				5,654,000				5,629,000	5,654,000
Ending Balance Collectively Evaluated for Impairment	637,385,000				620,113,000				637,385,000	620,113,000
Real Estate Construction [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				1,949,000				1,249,000	1,949,000	1,249,000
Charge-Offs									0	0
Recoveries									0	0
Provision									(306,000)	700,000
Ending Balance	1,643,000				1,949,000				1,643,000	1,949,000	1,249,000
Ending Balance Individually Evaluated for Impairment	0				0				0	0
Ending Balance Collectively Evaluated for Impairment	1,643,000				1,949,000				1,643,000	1,949,000
Loans & Leases [Abstract]
Ending Balance	185,741,000				115,644,000				185,741,000	115,644,000
Ending Balance Individually Evaluated for Impairment	0				0				0	0
Ending Balance Collectively Evaluated for Impairment	185,741,000				115,644,000				185,741,000	115,644,000
Residential 1st Mortgages [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				855,000				880,000	855,000	880,000
Charge-Offs									0	0
Recoveries									52,000	13,000
Provision									53,000	(38,000)
Ending Balance	960,000				855,000				960,000	855,000	880,000
Ending Balance Individually Evaluated for Impairment	117,000				118,000				117,000	118,000
Ending Balance Collectively Evaluated for Impairment	843,000				737,000				843,000	737,000
Loans & Leases [Abstract]
Ending Balance	299,379,000				255,253,000				299,379,000	255,253,000
Ending Balance Individually Evaluated for Impairment	2,365,000				2,368,000				2,365,000	2,368,000
Ending Balance Collectively Evaluated for Impairment	297,014,000				252,885,000				297,014,000	252,885,000
Home Equity Lines and Loans [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				2,675,000				2,761,000	2,675,000	2,761,000
Charge-Offs									(7,000)	0
Recoveries									78,000	28,000
Provision									(722,000)	(114,000)
Ending Balance	2,024,000				2,675,000				2,024,000	2,675,000	2,761,000
Ending Balance Individually Evaluated for Impairment	8,000				12,000				8,000	12,000
Ending Balance Collectively Evaluated for Impairment	2,016,000				2,663,000				2,016,000	2,663,000
Loans & Leases [Abstract]
Ending Balance	34,239,000				39,270,000				34,239,000	39,270,000
Ending Balance Individually Evaluated for Impairment	158,000				229,000				158,000	229,000
Ending Balance Collectively Evaluated for Impairment	34,081,000				39,041,000				34,081,000	39,041,000
Agricultural [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				8,076,000				8,242,000	8,076,000	8,242,000
Charge-Offs									0	0
Recoveries									0	0
Provision									(3,262,000)	(166,000)
Ending Balance	4,814,000				8,076,000				4,814,000	8,076,000	8,242,000
Ending Balance Individually Evaluated for Impairment	92,000				99,000				92,000	99,000
Ending Balance Collectively Evaluated for Impairment	4,722,000				7,977,000				4,722,000	7,977,000
Loans & Leases [Abstract]
Ending Balance	264,372,000				292,904,000				264,372,000	292,904,000
Ending Balance Individually Evaluated for Impairment	495,000				188,000				495,000	188,000
Ending Balance Collectively Evaluated for Impairment	263,877,000				292,716,000				263,877,000	292,716,000
Commercial [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				11,466,000				11,656,000	11,466,000	11,656,000
Charge-Offs									(1,101,000)	(592,000)
Recoveries									280,000	90,000
Provision									(684,000)	312,000
Ending Balance	9,961,000				11,466,000				9,961,000	11,466,000	11,656,000
Ending Balance Individually Evaluated for Impairment	20,000				137,000				20,000	137,000
Ending Balance Collectively Evaluated for Impairment	9,941,000				11,329,000				9,941,000	11,329,000
Loans & Leases [Abstract]
Ending Balance	374,816,000				384,795,000				374,816,000	384,795,000
Ending Balance Individually Evaluated for Impairment	233,000				1,528,000				233,000	1,528,000
Ending Balance Collectively Evaluated for Impairment	374,583,000				383,267,000				374,583,000	383,267,000
Consumer & Other [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				456,000				494,000	456,000	494,000
Charge-Offs									(66,000)	(83,000)
Recoveries									33,000	52,000
Provision									(90,000)	(7,000)
Ending Balance	333,000				456,000				333,000	456,000	494,000
Ending Balance Individually Evaluated for Impairment	52,000				61,000				52,000	61,000
Ending Balance Collectively Evaluated for Impairment	281,000				395,000				281,000	395,000
Loans & Leases [Abstract]
Ending Balance	235,529,000				15,422,000				235,529,000	15,422,000
Ending Balance Individually Evaluated for Impairment	254,000				200,000				254,000	200,000
Ending Balance Collectively Evaluated for Impairment	235,275,000				15,222,000				235,275,000	15,222,000
Leases [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				3,162,000				4,022,000	3,162,000	4,022,000
Charge-Offs									0	0
Recoveries									0	0
Provision									(1,431,000)	(860,000)
Ending Balance	1,731,000				3,162,000				1,731,000	3,162,000	4,022,000
Ending Balance Individually Evaluated for Impairment	0				0				0	0
Ending Balance Collectively Evaluated for Impairment	1,731,000				3,162,000				1,731,000	3,162,000
Loans & Leases [Abstract]
Ending Balance	103,522,000				105,402,000				103,522,000	105,402,000
Ending Balance Individually Evaluated for Impairment	0				0				0	0
Ending Balance Collectively Evaluated for Impairment	103,522,000				105,402,000				103,522,000	105,402,000
Unallocated [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance				$ 192,000				$ 261,000	192,000	261,000
Charge-Offs									0	0
Recoveries									0	0
Provision									892,000	(69,000)
Ending Balance	1,084,000				192,000				1,084,000	192,000	$ 261,000
Ending Balance Individually Evaluated for Impairment	0				0				0	0
Ending Balance Collectively Evaluated for Impairment	1,084,000				192,000				1,084,000	192,000
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	$ 876,000				$ 2,600,000				$ 876,000	$ 2,600,000