Effect of New Financial Accounting Standards (Details) - USD ($)		12 Months Ended
	Jan. 01, 2020	Dec. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings		$ 201,105,000	$ 190,212,000
Federal & state taxes, deferred		3,530,000	8,532,000
PCD assets		22,551,000
Allowance for credit losses on loans	$ 29,079,000	29,079,000	51,187,000	$ 29,652,000	$ 29,307,000
Liability for off-balance sheet credit exposures	0	0	5,800,000
Agricultural
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	3,748,000	3,748,000	1,146,000	3,691,000	3,637,000
Commercial and industrial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	8,394,000	8,394,000	19,309,000	7,594,000	7,478,000
Commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	13,804,000	13,804,000	23,138,000	14,798,000	15,635,000
Residential real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	2,685,000	2,685,000	6,425,000	3,272,000	2,349,000
Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	448,000	$ 448,000	$ 1,169,000	$ 297,000	$ 208,000
Impact of ASC 326 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	(5,400,000)
Federal & state taxes, deferred	1,900,000
PCD assets	(119,000)
Allowance for credit losses on loans	3,984,000
Liability for off-balance sheet credit exposures	3,433,000
Impact of ASC 326 Adoption | Agricultural
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	(2,557,000)
Impact of ASC 326 Adoption | Commercial and industrial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	2,728,000
Impact of ASC 326 Adoption | Commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	1,300,000
Impact of ASC 326 Adoption | Residential real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	2,050,000
Impact of ASC 326 Adoption | Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	463,000
As Reported Under ASC 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	33,063,000
Liability for off-balance sheet credit exposures	3,433,000
As Reported Under ASC 326 | Agricultural
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	1,191,000
As Reported Under ASC 326 | Commercial and industrial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	11,122,000
As Reported Under ASC 326 | Commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	15,104,000
As Reported Under ASC 326 | Residential real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	4,735,000
As Reported Under ASC 326 | Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans	$ 911,000