Allowance for Credit Losses, Aging Analysis of Loan & Lease Portfolio Including Unearned Income, Past Due (Details) - USD ($)	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 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	516,000	498,000	495,000
Total Loans & Leases	3,139,801,000	3,111,931,000	3,099,592,000
Interest income forgone on nonaccrual loans	35,700	15,530	22,000
Total Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	1,126,000	1,197,000	506,000
30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	610,000	699,000	11,000
60-89 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	0	0	0
Current [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	3,138,675,000	3,110,734,000	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	1,114,149,000	871,623,000	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	453,000	0	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	453,000	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	0	0
Commercial Real Estate [Member] | Current [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	1,113,696,000	871,623,000	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	498,000	495,000
Total Loans & Leases	656,337,000	639,172,000	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	498,000	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	656,318,000	638,674,000	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	178,451,000	186,623,000	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	85,000	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	85,000	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	178,451,000	186,538,000	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	309,728,000	293,489,000	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	102,000	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	102,000	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	309,626,000	293,489,000	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	31,664,000	35,875,000	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	31,664,000	35,875,000	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	497,000	0	0
Total Loans & Leases	235,085,000	252,031,000	264,372,000
Agricultural [Member] | Total Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	497,000	0	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	234,588,000	252,031,000	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	394,326,000	367,052,000	374,816,000
Commercial [Member] | Total Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	50,000	547,000	0
Commercial [Member] | 30-59 Days Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	50,000	547,000	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	394,276,000	366,505,000	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	129,665,000	359,697,000	235,529,000
Consumer & Other [Member] | Total Past Due [Member]
Aging Analysis of Loan & Lease Portfolio by Time Past Due [Abstract]
Total Loans & Leases	5,000	67,000	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	5,000	67,000	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	129,660,000	359,630,000	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	90,396,000	106,369,000	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	$ 90,396,000	$ 106,369,000	$ 103,522,000