Effect of New Financial Accounting Standards (Details) - USD ($) $ in Thousands		6 Months Ended	12 Months Ended
	Jan. 01, 2020	Jun. 30, 2020	Dec. 31, 2019	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings		$ 198,382	$ 201,105
Allowance for credit losses on loans	$ 29,079	55,644	29,079	$ 51,187	$ 28,691	$ 29,652	$ 29,307
Liability for off-balance sheet credit exposures	0	4,200
Federal & state taxes, deferred		$ 7,435	3,530
PCD assets			$ 22,551
Accounting standards update		us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201613Member
Agricultural
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	3,748	$ 1,408	$ 3,748	1,146	3,720	3,691	3,637
Commercial and industrial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	8,394	18,709	8,394	19,309	7,633	7,594	7,478
Commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	13,804	28,221	13,804	23,138	13,655	14,798	15,635
Residential real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	2,685	6,074	2,685	6,425	3,377	3,272	2,349
Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	448	$ 1,232	448	1,169	$ 306	$ 297	$ 208
Impact of ASC 326 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	(5,400)
Allowance for credit losses on loans	3,984		3,984
Liability for off-balance sheet credit exposures	3,433
Federal & state taxes, deferred	1,900
PCD assets	(119)
Impact of ASC 326 Adoption | Agricultural
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans			(2,557)	(2,557)
Impact of ASC 326 Adoption | Commercial and industrial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans			2,728	2,728
Impact of ASC 326 Adoption | Commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans			1,300	1,300
Impact of ASC 326 Adoption | Residential real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans			2,050	2,050
Impact of ASC 326 Adoption | Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans			$ 463	$ 463
As Reported Under ASC 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	33,063
Liability for off-balance sheet credit exposures	3,433
As Reported Under ASC 326 | Agricultural
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	1,191
As Reported Under ASC 326 | Commercial and industrial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	11,122
As Reported Under ASC 326 | Commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	15,104
As Reported Under ASC 326 | Residential real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	4,735
As Reported Under ASC 326 | Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	$ 911