Loans (Schedule of Carrying Amount of Loans with Deterioration of Credit Quality) (Details) - USD ($) $ in Thousands	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Total	$ 2,154,502	[1]	$ 2,001,415	[2]
Commercial and Industrial Loans
Financing Receivable, Recorded Investment [Line Items]
Total	488,058	[1]	458,538	[2]
Commercial Real Estate Loans
Financing Receivable, Recorded Investment [Line Items]
Total	929,040	[1]	858,030	[2]
Agricultural Loans
Financing Receivable, Recorded Investment [Line Items]
Total	337,801	[1]	306,946	[2]
Consumer Loans
Financing Receivable, Recorded Investment [Line Items]
Total	67,647	[1]	60,099	[2]
Residential Mortgage Loans
Financing Receivable, Recorded Investment [Line Items]
Total	179,199	[1]	183,770	[2]
Loans Acquired with Deteriorated Credit Quality
Financing Receivable, Recorded Investment [Line Items]
Total	9,117		11,048		$ 7,555
Carrying Amount, Net of Allowance	9,106		10,943		7,555
Loans Acquired with Deteriorated Credit Quality | Commercial and Industrial Loans
Financing Receivable, Recorded Investment [Line Items]
Total	988		1,656		1,325
Loans Acquired with Deteriorated Credit Quality | Commercial Real Estate Loans
Financing Receivable, Recorded Investment [Line Items]
Total	6,452		7,688		5,363
Loans Acquired with Deteriorated Credit Quality | Agricultural Loans
Financing Receivable, Recorded Investment [Line Items]
Total	789		706		0
Loans Acquired with Deteriorated Credit Quality | Consumer Loans
Financing Receivable, Recorded Investment [Line Items]
Total	0		53		0
Loans Acquired with Deteriorated Credit Quality | Residential Mortgage Loans
Financing Receivable, Recorded Investment [Line Items]
Total	$ 888		$ 945		$ 867

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

[2] Total recorded investment in loans includes $8,011 in accrued interest.