Loans (Schedule of Carrying Amount of Loans with Deterioration of Credit Quality) (Details) - USD ($) $ in Thousands	Sep. 30, 2018		Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	$ 2,351,277	[1]	$ 2,154,502	[2]
Commercial and Industrial Loans and Leases
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	529,464	[1]	488,058	[2]
Commercial Real Estate Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	988,575	[1]	929,040	[2]
Agricultural Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	363,954	[1]	337,801	[2]
Residential Mortgage Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	220,434	[1]	179,199	[2]
Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	7,599		9,117
Carrying Amount, Net of Allowance	7,564		9,106
Loans Acquired With Deteriorated Credit Quality | Commercial and Industrial Loans and Leases
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	1,189		988
Loans Acquired With Deteriorated Credit Quality | Commercial Real Estate Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	4,578		6,452
Loans Acquired With Deteriorated Credit Quality | Agricultural Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	972		789
Loans Acquired With Deteriorated Credit Quality | Residential Mortgage Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	$ 860		$ 888

[1] Total recorded investment in loans includes $11,104 in accrued interest.

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