Loans & Leases and Allowance for Credit Losses, Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	$ 3,111,931	$ 2,673,027	$ 2,617,122
Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	3,082,975	2,643,190	2,590,168
Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	8,080	13,621	11,606
Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	20,876	16,216	15,348
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:	871,623	838,570	816,668
Commercial Real Estate [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	861,874	831,941	814,560
Commercial Real Estate [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	5,239	6,629	2,108
Commercial Real Estate [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	4,510	0	0
Agricultural Real Estate [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	639,172	625,767	617,310
Agricultural Real Estate [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	624,859	611,792	602,781
Agricultural Real Estate [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	1,525	1,136	2,491
Agricultural Real Estate [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	12,788	12,839	12,038
Real Estate Construction [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	186,623	115,644	98,662
Real Estate Construction [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	186,623	115,644	98,662
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:	293,489	255,253	255,394
Residential 1st Mortgages [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	292,792	254,459	254,594
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:	697	794	800
Home Equity Lines and Loans [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	35,875	39,270	39,490
Home Equity Lines and Loans [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	35,691	39,092	39,374
Home Equity Lines and Loans [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	0	0	0
Home Equity Lines and Loans [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	184	178	116
Agricultural [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	252,031	292,904	289,182
Agricultural [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	251,108	289,276	284,211
Agricultural [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	0	2,617	4,168
Agricultural [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	923	1,011	803
Commercial [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	367,052	384,795	381,774
Commercial [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	364,465	380,650	377,779
Commercial [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	1,316	3,239	2,839
Commercial [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	1,271	906	1,156
Consumer & Other [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	359,697	15,422	16,871
Consumer & Other [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	359,194	14,934	16,436
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:	503	488	435
Leases [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	106,369	105,402	101,771
Leases [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases:	106,369	105,402	101,771
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