Loans (Schedule of Risk Category of Loans) (Details) - USD ($) $ in Thousands	Mar. 31, 2019		Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	$ 2,725,212	[1]	$ 2,744,042	[2]
Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	10,472		11,556
Loans Acquired With Deteriorated Credit Quality | Loans Acquired in Current Year
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income			481,901
Commercial and Industrial Loans and Leases
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	557,660	[1]	545,342	[2]
Commercial and Industrial Loans and Leases | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	902		1,038
Commercial Real Estate Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	1,215,532	[1]	1,211,882	[2]
Commercial Real Estate Loans | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	6,127		6,993
Agricultural Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	353,606	[1]	370,694	[2]
Agricultural Loans | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	1,798		1,877
Pass
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	2,005,703		1,996,743
Pass | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	289		0
Pass | Loans Acquired With Deteriorated Credit Quality | Loans Acquired in Current Year
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income			250,415
Pass | Commercial and Industrial Loans and Leases
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	529,641		517,497
Pass | Commercial Real Estate Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	1,174,789		1,165,937
Pass | Agricultural Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	301,273		313,309
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	70,621		75,247
Special Mention | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	1,438		1,436
Special Mention | Loans Acquired With Deteriorated Credit Quality | Loans Acquired in Current Year
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income			14,972
Special Mention | Commercial and Industrial Loans and Leases
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	8,155		7,541
Special Mention | Commercial Real Estate Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	24,998		26,723
Special Mention | Agricultural Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	37,468		40,983
Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	50,474		55,928
Substandard | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	7,100		8,472
Substandard | Loans Acquired With Deteriorated Credit Quality | Loans Acquired in Current Year
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income			11,521
Substandard | Commercial and Industrial Loans and Leases
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	19,864		20,304
Substandard | Commercial Real Estate Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	15,745		19,222
Substandard | Agricultural Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	14,865		16,402
Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	0		0
Doubtful | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	0		0
Doubtful | Loans Acquired With Deteriorated Credit Quality | Loans Acquired in Current Year
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income			0
Doubtful | Commercial and Industrial Loans and Leases
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	0		0
Doubtful | Commercial Real Estate Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	0		0
Doubtful | Agricultural Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	0		0
Total
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	2,126,798		2,127,918
Total | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	8,827		9,908
Total | Loans Acquired With Deteriorated Credit Quality | Loans Acquired in Current Year
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income			276,908
Total | Commercial and Industrial Loans and Leases
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	557,660		545,342
Total | Commercial Real Estate Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	1,215,532		1,211,882
Total | Agricultural Loans
Financing Receivable, Recorded Investment [Line Items]
Loans, net of deferred income	$ 353,606		$ 370,694

[1] Total recorded investment in loans includes $12,798 in accrued interest.

[2] Total recorded investment in loans includes $12,301 in accrued interest.