Loans, Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	$ 13,304	$ 11,941	$ 12,884	$ 11,190
Charge-offs	(34)	(48)	(387)	(225)
Recoveries	9	15	32	118
Provision (Credit)	400	475	1,150	1,300
Balance at end of period	13,679	12,383	13,679	12,383
Real Estate Loans [Member] | Residential [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	1,066	1,045	1,105	1,049
Charge-offs	(24)	(10)	(24)	(27)
Recoveries	0	1	0	70
Provision (Credit)	49	16	10	(40)
Balance at end of period	1,091	1,052	1,091	1,052
Real Estate Loans [Member] | Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	4,400	3,794	4,115	3,867
Charge-offs	0	(25)	(293)	(25)
Recoveries	0	0	0	3
Provision (Credit)	241	156	819	80
Balance at end of period	4,641	3,925	4,641	3,925
Real Estate Loans [Member] | Agricultural [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	4,532	3,673	4,264	3,143
Charge-offs	0		0	0
Recoveries	0		0
Provision (Credit)	180	256	448	786
Balance at end of period	4,712	3,929	4,712	3,929
Real Estate Loans [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	36	44	58	23
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision (Credit)	(17)	5	(39)	26
Balance at end of period	19	49	19	49
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	118	115	120	124
Charge-offs	(10)	(13)	(32)	(32)
Recoveries	6	9	24	26
Provision (Credit)	5	12	7	5
Balance at end of period	119	123	119	123
Other Commercial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	1,328	1,266	1,354	1,272
Charge-offs	0	0	(38)	(91)
Recoveries	3	5	8	19
Provision (Credit)	18	(52)	25	19
Balance at end of period	1,349	1,219	1,349	1,219
Other Agricultural Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	741	589	752	492
Charge-offs	0	0	0	(50)
Recoveries	0	0	0	0
Provision (Credit)	128	110	117	257
Balance at end of period	869	699	869	699
State and Political Subdivision Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	539	767	762	816
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision (Credit)	(3)	(16)	(226)	(65)
Balance at end of period	536	751	536	751
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	544	648	354	404
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision (Credit)	(201)	(12)	(11)	232
Balance at end of period	$ 343	$ 636	$ 343	$ 636