Loans & Leases and Allowance for Credit Losses, Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	$ 2,670,109	$ 2,673,027	$ 2,563,968
Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	2,643,302	2,643,190	2,534,567
Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	10,422	13,621	14,273
Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	16,385	16,216	15,128
Doubtful [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	0	0
Loss [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	0	0
Commercial Real Estate [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	861,311	838,570	815,366
Commercial Real Estate [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	854,346	831,941	813,090
Commercial Real Estate [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	6,965	6,629	2,276
Commercial Real Estate [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	0	0
Agricultural Real Estate [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	594,154	625,767	603,601
Agricultural Real Estate [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	580,205	611,792	587,444
Agricultural Real Estate [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	1,136	1,136	2,847
Agricultural Real Estate [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	12,813	12,839	13,310
Real Estate Construction [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	126,956	115,644	99,837
Real Estate Construction [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	126,956	115,644	99,837
Real Estate Construction [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	0	0
Real Estate Construction [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	0	0
Residential 1st Mortgages [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	256,732	255,253	258,359
Residential 1st Mortgages [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	256,027	254,459	257,878
Residential 1st Mortgages [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	0	0
Residential 1st Mortgages [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	705	794	481
Home Equity Lines & Loans [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	40,747	39,270	40,072
Home Equity Lines & Loans [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	40,577	39,092	40,028
Home Equity Lines & Loans [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	0	0
Home Equity Lines & Loans [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	170	178	44
Agricultural [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	264,771	292,904	257,004
Agricultural [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	263,794	289,276	250,630
Agricultural [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	2,617	6,167
Agricultural [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	977	1,011	207
Commercial [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	404,329	384,795	364,439
Commercial [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	400,735	380,650	360,525
Commercial [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	2,321	3,239	2,983
Commercial [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	1,273	906	931
Consumer & Other [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	14,839	15,422	18,418
Consumer & Other [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	14,392	14,934	18,263
Consumer & Other [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	0	0
Consumer & Other [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	447	488	155
Leases [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	106,270	105,402	106,872
Leases [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	106,270	105,402	106,872
Leases [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	0	0	0
Leases [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & leases	$ 0	$ 0	$ 0