Allowance for Credit Losses, Aging Analysis of Loan & Lease Portfolio Including Unearned Income, by the Time Past Due (Details) - USD ($)	6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	$ 0	$ 0	$ 0
Nonaccrual	548,000	473,000	495,000
Total Loans & Leases	3,033,196,000	3,064,512,000	3,099,592,000
Interest income forgone on nonaccrual loans	25,200	8,100	22,000
Total Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	586,000	828,000	506,000
30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	38,000	97,000	11,000
60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	258,000	0
Current [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	3,032,610,000	3,063,684,000	3,099,086,000
Commercial Real Estate [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	0	0	0
Nonaccrual	0	0	0
Total Loans & Leases	1,020,077,000	855,762,000	958,980,000
Commercial Real Estate [Member] | Total Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	258,000	0
Commercial Real Estate [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Commercial Real Estate [Member] | 60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	258,000	0
Commercial Real Estate [Member] | Current [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	1,020,077,000	855,504,000	958,980,000
Agricultural Real Estate [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	0	0	0
Nonaccrual	19,000	0	495,000
Total Loans & Leases	630,515,000	635,077,000	643,014,000
Agricultural Real Estate [Member] | Total Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	19,000	0	495,000
Agricultural Real Estate [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Agricultural Real Estate [Member] | 60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Agricultural Real Estate [Member] | Current [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	630,496,000	635,077,000	642,519,000
Real Estate Construction [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	0	0	0
Nonaccrual	0	0	0
Total Loans & Leases	170,933,000	166,548,000	185,741,000
Real Estate Construction [Member] | Total Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Real Estate Construction [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Real Estate Construction [Member] | 60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Real Estate Construction [Member] | Current [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	170,933,000	166,548,000	185,741,000
Residential 1st Mortgages [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	0	0	0
Nonaccrual	0	0	0
Total Loans & Leases	304,859,000	272,209,000	299,379,000
Residential 1st Mortgages [Member] | Total Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Residential 1st Mortgages [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Residential 1st Mortgages [Member] | 60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Residential 1st Mortgages [Member] | Current [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	304,859,000	272,209,000	299,379,000
Home Equity Lines & Loans [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	0	0	0
Nonaccrual	0	0	0
Total Loans & Leases	32,026,000	37,966,000	34,239,000
Home Equity Lines & Loans [Member] | Total Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Home Equity Lines & Loans [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Home Equity Lines & Loans [Member] | 60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Home Equity Lines & Loans [Member] | Current [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	32,026,000	37,966,000	34,239,000
Agricultural [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	0	0	0
Nonaccrual	529,000	473,000	0
Total Loans & Leases	236,436,000	261,986,000	264,372,000
Agricultural [Member] | Total Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	529,000	473,000	0
Agricultural [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Agricultural [Member] | 60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Agricultural [Member] | Current [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	235,907,000	261,513,000	264,372,000
Commercial [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	0	0	0
Nonaccrual	0	0	0
Total Loans & Leases	361,432,000	369,817,000	374,816,000
Commercial [Member] | Total Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Commercial [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Commercial [Member] | 60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Commercial [Member] | Current [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	361,432,000	369,817,000	374,816,000
Consumer & Other [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	0	0	0
Nonaccrual	0	0	0
Total Loans & Leases	177,042,000	361,035,000	235,529,000
Consumer & Other [Member] | Total Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	38,000	97,000	11,000
Consumer & Other [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	38,000	97,000	11,000
Consumer & Other [Member] | 60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Consumer & Other [Member] | Current [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	177,004,000	360,938,000	235,518,000
Leases [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
90 Days and Still Accruing	0	0	0
Nonaccrual	0	0	0
Total Loans & Leases	99,876,000	104,112,000	103,522,000
Leases [Member] | Total Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Leases [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Leases [Member] | 60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Leases [Member] | Current [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	$ 99,876,000	$ 104,112,000	$ 103,522,000