Loans (Schedule of Aging of Recorded Investment in Loans) (Details) - USD ($) $ in Thousands	Sep. 30, 2019		Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Total	$ 3,074,146	[1]	$ 2,744,042	[2]
Total Past Due	14,652	[1]	21,364	[2]
Loans Not Past Due	3,059,494	[1]	2,722,678	[2]
Accrued interest included in recorded investment	13,404		12,301
Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total	14,300		11,556
Total Past Due	1,430		2,592
Loans Not Past Due	12,870		8,964
Loans Acquired With Deteriorated Credit Quality | Loans Acquired in Current Year
Financing Receivable, Past Due [Line Items]
Total	338,803		481,901
Total Past Due	719		6,382
Loans Not Past Due	338,084		475,519
Commercial and Industrial Loans and Leases
Financing Receivable, Past Due [Line Items]
Total	580,240	[1]	545,342	[2]
Total Past Due	2,731		5,669
Loans Not Past Due	577,509		539,673
Commercial and Industrial Loans and Leases | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total	1,693		1,038
Commercial Real Estate Loans
Financing Receivable, Past Due [Line Items]
Total	1,481,155	[1]	1,211,882	[2]
Total Past Due	2,642		4,505
Loans Not Past Due	1,478,513		1,207,377
Commercial Real Estate Loans | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total	8,938		6,993
Agricultural Loans
Financing Receivable, Past Due [Line Items]
Total	393,033	[1]	370,694	[2]
Total Past Due	414		1,642
Loans Not Past Due	392,619		369,052
Agricultural Loans | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total	2,611		1,877
Home Equity Loans
Financing Receivable, Past Due [Line Items]
Total	223,658	[1]	209,009	[2]
Total Past Due	1,327		656
Loans Not Past Due	222,331		208,353
Home Equity Loans | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total	371		365
Consumer Loans
Financing Receivable, Past Due [Line Items]
Total	82,633	[1]	77,761	[2]
Total Past Due	416		1,214
Loans Not Past Due	82,217		76,547
Consumer Loans | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total	0		0
Residential Mortgage Loans
Financing Receivable, Past Due [Line Items]
Total	313,427	[1]	329,354	[2]
Total Past Due	7,122		7,678
Loans Not Past Due	306,305		321,676
Residential Mortgage Loans | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total	687		1,283
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	8,867	[1]	12,958	[2]
30-59 Days Past Due | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total Past Due	372		448
30-59 Days Past Due | Loans Acquired With Deteriorated Credit Quality | Loans Acquired in Current Year
Financing Receivable, Past Due [Line Items]
Total Past Due	507		2,571
30-59 Days Past Due | Commercial and Industrial Loans and Leases
Financing Receivable, Past Due [Line Items]
Total Past Due	1,653		5,414
30-59 Days Past Due | Commercial Real Estate Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	0		768
30-59 Days Past Due | Agricultural Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	414		563
30-59 Days Past Due | Home Equity Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	1,137		471
30-59 Days Past Due | Consumer Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	255		971
30-59 Days Past Due | Residential Mortgage Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	5,408		4,771
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	2,649	[1]	3,432	[2]
60-89 Days Past Due | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total Past Due	0		885
60-89 Days Past Due | Loans Acquired With Deteriorated Credit Quality | Loans Acquired in Current Year
Financing Receivable, Past Due [Line Items]
Total Past Due	212		1,620
60-89 Days Past Due | Commercial and Industrial Loans and Leases
Financing Receivable, Past Due [Line Items]
Total Past Due	966		183
60-89 Days Past Due | Commercial Real Estate Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	636		705
60-89 Days Past Due | Agricultural Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	0		805
60-89 Days Past Due | Home Equity Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	112		125
60-89 Days Past Due | Consumer Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	107		94
60-89 Days Past Due | Residential Mortgage Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	828		1,520
90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	3,136	[1]	4,974	[2]
90 Days or More Past Due | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total Past Due	1,058		1,259
90 Days or More Past Due | Loans Acquired With Deteriorated Credit Quality | Loans Acquired in Current Year
Financing Receivable, Past Due [Line Items]
Total Past Due	0		2,191
90 Days or More Past Due | Commercial and Industrial Loans and Leases
Financing Receivable, Past Due [Line Items]
Total Past Due	112		72
90 Days or More Past Due | Commercial Real Estate Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	2,006		3,032
90 Days or More Past Due | Agricultural Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	0		274
90 Days or More Past Due | Home Equity Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	78		60
90 Days or More Past Due | Consumer Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	54		149
90 Days or More Past Due | Residential Mortgage Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 886		$ 1,387

[1] Total recorded investment in loans includes $13,404 in accrued interest.

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