Loans (Schedule of Carrying Amount of Loans with Deterioration of Credit Quality) (Details) - USD ($) $ in Thousands	Mar. 31, 2018		Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	$ 2,163,545	[1]	$ 2,154,502	[2]
Commercial and Industrial Loans and Leases
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	483,512	[1]	488,058	[2]
Commercial Real Estate Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	950,326	[1]	929,040	[2]
Agricultural Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	333,988	[1]	337,801	[2]
Residential Mortgage Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	178,537	[1]	179,199	[2]
Receivables Acquired with Deteriorated Credit Quality
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	8,819		9,117
Carrying Amount, Net of Allowance	8,778		9,106
Receivables Acquired with Deteriorated Credit Quality | Commercial and Industrial Loans and Leases
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	790		988
Receivables Acquired with Deteriorated Credit Quality | Commercial Real Estate Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	6,194		6,452
Receivables Acquired with Deteriorated Credit Quality | Agricultural Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	957		789
Receivables Acquired with Deteriorated Credit Quality | Residential Mortgage Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	$ 878		$ 888

[1] Total recorded investment in loans includes $9,697 in accrued interest.

[2] Total recorded investment in loans includes $9,483 in accrued interest.