Allowance for Credit Losses, Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings (Details) - USD ($) $ in Thousands	Jun. 30, 2021		Dec. 31, 2020		Jun. 30, 2020
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	$ 3,033,196		$ 3,099,592		$ 3,064,512
Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	2,997,685	[1]	3,071,556	[2]	3,032,294	[3]
Watch [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	907,200		958,200		887,800
Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	17,008		9,405		11,139
Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	18,503		18,631		21,079
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	1,020,077		958,980		855,762
Commercial Real Estate [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	1,004,715	[1]	946,621	[2]	843,952	[3]
Commercial Real Estate [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	5,990		7,849		7,300
Commercial Real Estate [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	9,372		4,510		4,510
Agricultural Real Estate [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	630,515		643,014		635,077
Agricultural Real Estate [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	621,165	[1]	631,043	[2]	620,754	[3]
Agricultural Real Estate [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	2,811		400		1,530
Agricultural Real Estate [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	6,539		11,571		12,793
Real Estate Construction [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	170,933		185,741		166,548
Real Estate Construction [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	170,933	[1]	185,741	[2]	166,548	[3]
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	304,859		299,379		272,209
Residential 1st Mortgages [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	304,089	[1]	298,689	[2]	271,507	[3]
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	770		690		702
Home Equity Lines and Loans [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	32,026		34,239		37,966
Home Equity Lines and Loans [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	31,848	[1]	34,058	[2]	37,780	[3]
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	178		181		186
Agricultural [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	236,436		264,372		261,986
Agricultural [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	235,716	[1]	263,781	[2]	261,085	[3]
Agricultural [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	64		96		0
Agricultural [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	656		495		901
Commercial [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	361,432		374,816		369,817
Commercial [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	352,598	[1]	373,038	[2]	366,204	[3]
Commercial [Member] | Special Mention [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	8,143		1,060		2,309
Commercial [Member] | Substandard [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	691		718		1,304
Consumer & Other [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	177,042		235,529		361,035
Consumer & Other [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	176,745	[1]	235,063	[2]	360,352	[3]
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	297		466		683
Leases [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	99,876		103,522		104,112
Leases [Member] | Pass [Member]
Loan & Lease Portfolio Allocated by Management's Internal Risk Ratings [Abstract]
Loans & Leases	99,876	[1]	103,522	[2]	104,112	[3]
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

[1] Includes “Watch” loans of $907.2 million.

[2] Includes “Watch” loans of $958.2 million.

[3] Includes “Watch” loans of $887.8 million.