Loans & Leases and Allowance for Credit Losses, Allocation of Allowance For Credit Losses by Portfolio Segment and By Impairment Methodology (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Allowance for Credit Losses [Roll Forward]
Beginning Balance	$ 55,012	$ 55,266	$ 55,266
Charge-Offs	(265)	(400)	(675)
Recoveries	77	41	221
Provision	0	0	200
Ending Balance	54,824	54,907	55,012
Ending Balance Individually Evaluated for Impairment	595	627	661
Ending Balance Collectively Evaluated for Impairment	54,229	54,280	54,351
Loans & Leases [Abstract]
Ending Balance	2,670,109	2,563,968	2,673,027
Ending Balance Individually Evaluated for Impairment	15,071	16,397	14,691
Ending Balance Collectively Evaluated for Impairment	2,655,038	2,547,571	2,658,336
Commercial Real Estate [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	11,053	11,609	11,609
Charge-Offs	0	0	0
Recoveries	0	0	0
Provision	69	(209)	(556)
Ending Balance	11,122	11,400	11,053
Ending Balance Individually Evaluated for Impairment	0	214	234
Ending Balance Collectively Evaluated for Impairment	11,122	11,186	10,819
Loans & Leases [Abstract]
Ending Balance	861,311	815,366	838,570
Ending Balance Individually Evaluated for Impairment	4,486	4,638	4,524
Ending Balance Collectively Evaluated for Impairment	856,825	810,728	834,046
Agricultural Real Estate [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	15,128	14,092	14,092
Charge-Offs	0	0	0
Recoveries	0	6	38
Provision	(659)	395	998
Ending Balance	14,469	14,493	15,128
Ending Balance Individually Evaluated for Impairment	0	0	0
Ending Balance Collectively Evaluated for Impairment	14,469	14,493	15,128
Loans & Leases [Abstract]
Ending Balance	594,154	603,601	625,767
Ending Balance Individually Evaluated for Impairment	5,629	7,238	5,654
Ending Balance Collectively Evaluated for Impairment	588,525	596,363	620,113
Real Estate Construction [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	1,949	1,249	1,249
Charge-Offs	0	0	0
Recoveries	0	0	0
Provision	(22)	(42)	700
Ending Balance	1,927	1,207	1,949
Ending Balance Individually Evaluated for Impairment	0	0	0
Ending Balance Collectively Evaluated for Impairment	1,927	1,207	1,949
Loans & Leases [Abstract]
Ending Balance	126,956	99,837	115,644
Ending Balance Individually Evaluated for Impairment	0	0	0
Ending Balance Collectively Evaluated for Impairment	126,956	99,837	115,644
Residential 1st Mortgages [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	855	880	880
Charge-Offs	0	0	0
Recoveries	19	3	13
Provision	163	(20)	(38)
Ending Balance	1,037	863	855
Ending Balance Individually Evaluated for Impairment	116	124	118
Ending Balance Collectively Evaluated for Impairment	921	739	737
Loans & Leases [Abstract]
Ending Balance	256,732	258,359	255,253
Ending Balance Individually Evaluated for Impairment	2,310	2,469	2,368
Ending Balance Collectively Evaluated for Impairment	254,422	255,890	252,885
Home Equity Lines & Loans [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	2,675	2,761	2,761
Charge-Offs	0	0	0
Recoveries	20	6	28
Provision	88	(29)	(114)
Ending Balance	2,783	2,738	2,675
Ending Balance Individually Evaluated for Impairment	10	13	12
Ending Balance Collectively Evaluated for Impairment	2,773	2,725	2,663
Loans & Leases [Abstract]
Ending Balance	40,747	40,072	39,270
Ending Balance Individually Evaluated for Impairment	200	255	229
Ending Balance Collectively Evaluated for Impairment	40,547	39,817	39,041
Agricultural [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	8,076	8,242	8,242
Charge-Offs	0	0	0
Recoveries	28	0	0
Provision	(1,145)	(794)	(166)
Ending Balance	6,959	7,448	8,076
Ending Balance Individually Evaluated for Impairment	398	98	99
Ending Balance Collectively Evaluated for Impairment	6,561	7,350	7,977
Loans & Leases [Abstract]
Ending Balance	264,771	257,004	292,904
Ending Balance Individually Evaluated for Impairment	733	200	188
Ending Balance Collectively Evaluated for Impairment	264,038	256,804	292,716
Commercial [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	11,466	11,656	11,656
Charge-Offs	(244)	(379)	(592)
Recoveries	2	12	90
Provision	990	644	312
Ending Balance	12,214	11,933	11,466
Ending Balance Individually Evaluated for Impairment	11	172	137
Ending Balance Collectively Evaluated for Impairment	12,203	11,761	11,329
Loans & Leases [Abstract]
Ending Balance	404,329	364,439	384,795
Ending Balance Individually Evaluated for Impairment	1,517	1,591	1,528
Ending Balance Collectively Evaluated for Impairment	402,812	362,848	383,267
Consumer & Other [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	456	494	494
Charge-Offs	(21)	(21)	(83)
Recoveries	8	14	52
Provision	(61)	(20)	(7)
Ending Balance	382	467	456
Ending Balance Individually Evaluated for Impairment	60	6	61
Ending Balance Collectively Evaluated for Impairment	322	461	395
Loans & Leases [Abstract]
Ending Balance	14,839	18,418	15,422
Ending Balance Individually Evaluated for Impairment	196	6	200
Ending Balance Collectively Evaluated for Impairment	14,643	18,412	15,222
Leases [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	3,162	4,022	4,022
Charge-Offs	0	0	0
Recoveries	0	0	0
Provision	26	(14)	(860)
Ending Balance	3,188	4,008	3,162
Ending Balance Individually Evaluated for Impairment	0	0	0
Ending Balance Collectively Evaluated for Impairment	3,188	4,008	3,162
Loans & Leases [Abstract]
Ending Balance	106,270	106,872	105,402
Ending Balance Individually Evaluated for Impairment	0	0	0
Ending Balance Collectively Evaluated for Impairment	106,270	106,872	105,402
Unallocated [Member]
Allowance for Credit Losses [Roll Forward]
Beginning Balance	192	261	261
Charge-Offs	0	0	0
Recoveries	0	0	0
Provision	551	89	(69)
Ending Balance	743	350	192
Ending Balance Individually Evaluated for Impairment	0	0	0
Ending Balance Collectively Evaluated for Impairment	743	350	192
Loans & Leases [Abstract]
Ending Balance	0	0	0
Ending Balance Individually Evaluated for Impairment	0	0	0
Ending Balance Collectively Evaluated for Impairment	0	0	0
Restructured Loans [Member]
Loans & Leases [Abstract]
Ending Balance Individually Evaluated for Impairment	$ 2,500	$ 2,700	$ 2,600

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

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- Definition

Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

+ References

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- Definition

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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- Definition

The balance of financing receivables that were collectively evaluated for impairment.

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The balance of financing receivables that were individually evaluated for impairment.

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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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- Definition

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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- Definition

Amount of expense related to estimated loss from loan and lease transactions.

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