Loans (Schedule of Aging of Recorded Investment in Loans) (Details) - USD ($) $ in Thousands	Jun. 30, 2019		Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Total	$ 2,732,452	[1]	$ 2,744,042	[2]
Total Past Due	15,519	[1]	21,364	[2]
Loans Not Past Due	2,716,933	[1]	2,722,678	[2]
Accrued interest included in recorded investment	11,778		12,301
Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total	10,029		11,556
Total Past Due	1,860		2,592
Loans Not Past Due	8,169		8,964
Loans Acquired With Deteriorated Credit Quality | Loans Acquired in Current Year
Financing Receivable, Past Due [Line Items]
Total			481,901
Total Past Due			6,382
Loans Not Past Due			475,519
Commercial and Industrial Loans and Leases
Financing Receivable, Past Due [Line Items]
Total	555,935	[1]	545,342	[2]
Total Past Due	800		5,669
Loans Not Past Due	555,135		539,673
Commercial and Industrial Loans and Leases | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total	882		1,038
Commercial Real Estate Loans
Financing Receivable, Past Due [Line Items]
Total	1,216,906	[1]	1,211,882	[2]
Total Past Due	3,496		4,505
Loans Not Past Due	1,213,410		1,207,377
Commercial Real Estate Loans | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total	5,629		6,993
Agricultural Loans
Financing Receivable, Past Due [Line Items]
Total	368,912	[1]	370,694	[2]
Total Past Due	2,472		1,642
Loans Not Past Due	366,440		369,052
Agricultural Loans | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total	1,882		1,877
Home Equity Loans
Financing Receivable, Past Due [Line Items]
Total	204,350	[1]	209,009	[2]
Total Past Due	911		656
Loans Not Past Due	203,439		208,353
Home Equity Loans | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total	368		365
Consumer Loans
Financing Receivable, Past Due [Line Items]
Total	77,824	[1]	77,761	[2]
Total Past Due	819		1,214
Loans Not Past Due	77,005		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	308,525	[1]	329,354	[2]
Total Past Due	7,021		7,678
Loans Not Past Due	301,504		321,676
Residential Mortgage Loans | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total	1,268		1,283
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	9,691	[1]	12,958	[2]
30-59 Days Past Due | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total Past Due	860		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			2,571
30-59 Days Past Due | Commercial and Industrial Loans and Leases
Financing Receivable, Past Due [Line Items]
Total Past Due	298		5,414
30-59 Days Past Due | Commercial Real Estate Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	1,562		768
30-59 Days Past Due | Agricultural Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	1,857		563
30-59 Days Past Due | Home Equity Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	609		471
30-59 Days Past Due | Consumer Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	690		971
30-59 Days Past Due | Residential Mortgage Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	4,675		4,771
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	2,118	[1]	3,432	[2]
60-89 Days Past Due | Loans Acquired With Deteriorated Credit Quality
Financing Receivable, Past Due [Line Items]
Total Past Due	26		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			1,620
60-89 Days Past Due | Commercial and Industrial Loans and Leases
Financing Receivable, Past Due [Line Items]
Total Past Due	47		183
60-89 Days Past Due | Commercial Real Estate Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	467		705
60-89 Days Past Due | Agricultural Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	180		805
60-89 Days Past Due | Home Equity Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	213		125
60-89 Days Past Due | Consumer Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	46		94
60-89 Days Past Due | Residential Mortgage Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	1,165		1,520
90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Total Past Due	3,710	[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	974		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			2,191
90 Days or More Past Due | Commercial and Industrial Loans and Leases
Financing Receivable, Past Due [Line Items]
Total Past Due	455		72
90 Days or More Past Due | Commercial Real Estate Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	1,467		3,032
90 Days or More Past Due | Agricultural Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	435		274
90 Days or More Past Due | Home Equity Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	89		60
90 Days or More Past Due | Consumer Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	83		149
90 Days or More Past Due | Residential Mortgage Loans
Financing Receivable, Past Due [Line Items]
Total Past Due	$ 1,181		$ 1,387

[1] Total recorded investment in loans includes $11,778 in accrued interest.

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