Allowance for Credit Losses, Loan Portfolio Allocated by Management's Internal Credit Ratings (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	$ 2,673,027	$ 2,571,241
Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	2,643,190	2,543,255
Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	13,621	12,865
Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	16,216	15,121
Doubtful [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	0
Loss [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	0
Commercial Real Estate [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	838,570	826,549
Commercial Real Estate [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	831,941	823,983
Commercial Real Estate [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	6,629	2,566
Commercial Real Estate [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	0
Agricultural Real Estate [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	625,767	584,625
Agricultural Real Estate [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	611,792	566,612
Agricultural Real Estate [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	1,136	4,703
Agricultural Real Estate [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	12,839	13,310
Real Estate Construction [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	115,644	98,568
Real Estate Construction [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	115,644	98,568
Real Estate Construction [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	0
Real Estate Construction [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	0
Residential 1st Mortgages [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	255,253	259,736
Residential 1st Mortgages [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	254,459	259,208
Residential 1st Mortgages [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	0
Residential 1st Mortgages [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	794	528
Home Equity Lines and Loans [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	39,270	40,789
Home Equity Lines and Loans [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	39,092	40,744
Home Equity Lines and Loans [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	0
Home Equity Lines and Loans [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	178	45
Agricultural [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	292,904	290,463
Agricultural [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	289,276	284,561
Agricultural [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	2,617	5,433
Agricultural [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	1,011	469
Commercial [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	384,795	343,834
Commercial [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	380,650	343,085
Commercial [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	3,239	163
Commercial [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	906	586
Consumer & Other [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	15,422	19,412
Consumer & Other [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	14,934	19,229
Consumer & Other [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	0
Consumer & Other [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	488	183
Leases [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	105,402	107,265
Leases [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	105,402	107,265
Leases [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	0
Leases [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	$ 0	$ 0