Loans and Allowance for Loan Losses (Details)		3 Months Ended		12 Months Ended
	Jan. 01, 2020 USD ($)	Mar. 31, 2020 USD ($) alternative	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Modifications Performing Recorded Investment		$ 2,676,000	$ 2,100,000	$ 2,701,000
Gross loans		2,745,130,000		2,699,164,000
Loans Receivable Held-for-sale, Amount		1,251,000		1,820,000
loans and leases receivable gross excluding loans held for sale		2,743,879,000		2,697,344,000
Less [Abstract]
Net deferred loan fees, premiums and discounts		832,000		3,817,000
Net loans		2,710,171,000		2,666,616,000
Loans And Leases Receivable, Interest Receivable		12,500,000		12,300,000
Impaired Loans [Abstract]
Minimum value of loans individually measured for impairment		$ 250,000
Number of alternatives for measuring impaired loans receivable | alternative		3
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	$ 28,583,000	$ 32,876,000	26,704,000	26,911,000	$ 26,189,000
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease)		5,481,000	947,000	6,433,000
Provision for Loan and Lease Losses		5,481,000	947,000
Losses charged off		(1,423,000)	(568,000)	(6,326,000)
Recoveries		235,000	136,000	615,000
Ending Balance [Abstract]
Loans and Leases Receivable, Including Held for Sale, Net of Deferred Income		2,744,298,000		2,695,347,000
Loans By Collateral Type [Abstract]
Specific Allowance		1,831,000		1,098,000
Financing Receivable, Individually Evaluated for Impairment		18,543,000
Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans		123,346,000		94,462,000
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	1,033,000	1,620,000	552,000	1,146,000	561,000
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease)		587,000	(9,000)	585,000
Losses charged off		0	0	0
Recoveries		0	0	0
Ending Balance [Abstract]
Loans and Leases Receivable, Including Held for Sale, Net of Deferred Income		123,326,000		94,142,000
Loans By Collateral Type [Abstract]
Specific Allowance		269,000		0
Financing Receivable, Individually Evaluated for Impairment		540,000
Agricultural real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans		242,541,000		240,481,000
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	1,323,000	1,335,000	1,282,000	1,093,000	1,246,000
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease)		12,000	36,000	(153,000)
Losses charged off		0	0	0
Recoveries		0	0	0
Ending Balance [Abstract]
Loans and Leases Receivable, Including Held for Sale, Net of Deferred Income		242,891,000		240,241,000
Loans By Collateral Type [Abstract]
Specific Allowance		0		0
Financing Receivable, Individually Evaluated for Impairment		150,000
1-4 Family residential properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Modifications Performing Recorded Investment		1,366,000		1,382,000
Gross loans		325,146,000		336,553,000
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	2,142,000	1,931,000	1,341,000	1,386,000	1,504,000
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease)		(77,000)	(41,000)	1,268,000
Losses charged off		(196,000)	(130,000)	(1,477,000)
Recoveries		62,000	8,000	91,000
Ending Balance [Abstract]
Loans and Leases Receivable, Including Held for Sale, Net of Deferred Income		325,128,000		336,427,000
Loans By Collateral Type [Abstract]
Specific Allowance		203,000		182,000
Financing Receivable, Individually Evaluated for Impairment		$ 3,875,000
Period When Loans are Charged-down		180 days
Commercial Real Estate Including Multifamily
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss		$ 13,621,000	10,565,000	11,198,000	11,102,000
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease)		1,961,000	(481,000)	1,827,000
Losses charged off		(84,000)	(56,000)	(1,743,000)
Recoveries		5,000	0	12,000
Ending Balance [Abstract]
Loans and Leases Receivable, Including Held for Sale, Net of Deferred Income		1,142,602,000		1,149,650,000
Multifamily residential properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans		140,536,000		155,132,000
Ending Balance [Abstract]
Loans and Leases Receivable, Including Held for Sale, Net of Deferred Income		139,734,000		153,948,000
Loans By Collateral Type [Abstract]
Specific Allowance		17,000		19,000
Financing Receivable, Individually Evaluated for Impairment		3,060,000
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Modifications Performing Recorded Investment		1,140,000		1,146,000
Gross loans		$ 1,003,021,000		997,175,000
Loans Receivable Additional Information [Abstract]
Debt coverage ratio		1.20x
Amortization period of loans		twenty years
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	11,739,000			11,198,000
Ending Balance [Abstract]
Loans and Leases Receivable, Including Held for Sale, Net of Deferred Income		$ 1,002,868,000		995,702,000
Loans By Collateral Type [Abstract]
Specific Allowance		1,029,000		587,000
Financing Receivable, Individually Evaluated for Impairment		$ 6,494,000
Commercial real estate | Minimum [Member]
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)		65.00%
Commercial real estate | Maximum [Member]
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)		80.00%
Loans secured by real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Modifications Performing Recorded Investment		$ 2,506,000		2,528,000
Gross loans		1,834,590,000		1,823,803,000
Ending Balance [Abstract]
Loans and Leases Receivable, Including Held for Sale, Net of Deferred Income		1,833,947,000		1,820,460,000
Loans By Collateral Type [Abstract]
Specific Allowance		1,518,000		788,000
Financing Receivable, Individually Evaluated for Impairment		14,119,000
Agricultural loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans		139,014,000		136,023,000
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	1,023,000	1,064,000	1,130,000	1,386,000	951,000
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease)		41,000	188,000	459,000
Losses charged off		0	(9,000)	(24,000)
Recoveries		0	0	0
Ending Balance [Abstract]
Loans and Leases Receivable, Including Held for Sale, Net of Deferred Income		139,136,000		136,124,000
Loans By Collateral Type [Abstract]
Specific Allowance		0		8,000
Financing Receivable, Individually Evaluated for Impairment		279,000
Commercial Including Other
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss		11,294,000	10,830,000	9,273,000	9,893,000
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease)		2,815,000	1,013,000	1,053,000
Losses charged off		(972,000)	(104,000)	(1,828,000)
Recoveries		23,000	28,000	155,000
Ending Balance [Abstract]
Loans and Leases Receivable, Including Held for Sale, Net of Deferred Income		689,111,000		655,580,000
Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Modifications Performing Recorded Investment		125,000		128,000
Gross loans		$ 565,714,000		528,987,000
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)		80.00%
Amortization period of loans		seven years
Loans Receivable, Time Period		one year
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	9,428,000			9,273,000
Ending Balance [Abstract]
Loans and Leases Receivable, Including Held for Sale, Net of Deferred Income		$ 565,789,000		528,973,000
Loans By Collateral Type [Abstract]
Specific Allowance		312,000		301,000
Financing Receivable, Individually Evaluated for Impairment		4,134,000
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Modifications Performing Recorded Investment		4,000		5,000
Gross loans		82,330,000		83,544,000
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	1,895,000	2,011,000	1,004,000	1,429,000	$ 932,000
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease)		142,000	241,000	1,394,000
Losses charged off		(171,000)	(269,000)	(1,254,000)
Recoveries		145,000	$ 100,000	357,000
Ending Balance [Abstract]
Loans and Leases Receivable, Including Held for Sale, Net of Deferred Income		82,104,000		83,183,000
Loans By Collateral Type [Abstract]
Specific Allowance		1,000		1,000
Financing Receivable, Individually Evaluated for Impairment		11,000
All other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans		123,482,000		126,807,000
Ending Balance [Abstract]
Loans and Leases Receivable, Including Held for Sale, Net of Deferred Income		123,322,000		126,607,000
Agricultural and Farm Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans		381,600,000		376,400,000
Increase (Decrease) in Accounts and Notes Receivable		$ 5,200,000
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)		65.00%
Amortization period of loans		twenty five years
Loans Receivable, Time Period		one year
Corn And Other Grain Farming [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans		$ 309,400,000		301,500,000
Increase (Decrease) in Accounts and Notes Receivable		7,900,000
Motels and Hotels Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans		119,700,000
Non-residential Buildings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans		294,600,000
Residential Buildings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans		280,900,000
Nursing Care Facilities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans		108,700,000
Other Gambling Industries [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans		$ 123,400,000
Unsecured Open-end Loans [Member]
Loans By Collateral Type [Abstract]
Period When Loans are Charged-down		180 days
Other Secured Loans [Member]
Loans By Collateral Type [Abstract]
Period When Loans are Charged-down		120 days
Residential Real Estate
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)		80.00%
Amortization period of loans		twenty five years
Balloon period		five years
Financial Asset Acquired with Credit Deterioration [Member]
Less [Abstract]
Net loans				4,586,000
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	1,198,000			365,000
Ending Balance [Abstract]
Financing Receivable, after Allowance for Credit Loss				4,951,000
Financial Asset Acquired with Credit Deterioration [Member] | Construction and land development
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	291,000			0
Ending Balance [Abstract]
Financing Receivable, after Allowance for Credit Loss				256,000
Financial Asset Acquired with Credit Deterioration [Member] | Agricultural real estate
Ending Balance [Abstract]
Financing Receivable, after Allowance for Credit Loss				0
Financial Asset Acquired with Credit Deterioration [Member] | 1-4 Family residential properties
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	48,000			6,000
Ending Balance [Abstract]
Financing Receivable, after Allowance for Credit Loss				371,000
Financial Asset Acquired with Credit Deterioration [Member] | Multifamily residential properties
Ending Balance [Abstract]
Financing Receivable, after Allowance for Credit Loss				2,077,000
Financial Asset Acquired with Credit Deterioration [Member] | Commercial real estate
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	818,000			359,000
Financial Asset Acquired with Credit Deterioration [Member] | Agricultural loans
Ending Balance [Abstract]
Financing Receivable, after Allowance for Credit Loss				0
Financial Asset Acquired with Credit Deterioration [Member] | Commercial and industrial loans
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	41,000			0
Ending Balance [Abstract]
Financing Receivable, after Allowance for Credit Loss				0
Financial Asset Acquired with Credit Deterioration [Member] | Consumer loans
Ending Balance [Abstract]
Financing Receivable, after Allowance for Credit Loss				$ 0
Loans secured by real estate
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		$ 14,685,000
Loans secured by real estate | Construction and land development
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		540,000
Loans secured by real estate | Agricultural real estate
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		150,000
Loans secured by real estate | 1-4 Family residential properties
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		3,875,000
Loans secured by real estate | Multifamily residential properties
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		3,060,000
Loans secured by real estate | Commercial real estate
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		6,494,000
Loans secured by real estate | Loans secured by real estate
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		14,119,000
Loans secured by real estate | Agricultural loans
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		239,000
Loans secured by real estate | Commercial and industrial loans
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		327,000
Loans secured by real estate | Consumer loans
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		0
Business Assets [Member]
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		3,828,000
Business Assets [Member] | Construction and land development
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		0
Business Assets [Member] | Agricultural real estate
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		0
Business Assets [Member] | 1-4 Family residential properties
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		0
Business Assets [Member] | Multifamily residential properties
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		0
Business Assets [Member] | Commercial real estate
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		0
Business Assets [Member] | Loans secured by real estate
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		0
Business Assets [Member] | Agricultural loans
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		40,000
Business Assets [Member] | Commercial and industrial loans
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		3,788,000
Business Assets [Member] | Consumer loans
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		0
Other Property [Member]
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		30,000
Other Property [Member] | Construction and land development
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		0
Other Property [Member] | Agricultural real estate
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		0
Other Property [Member] | 1-4 Family residential properties
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		0
Other Property [Member] | Multifamily residential properties
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		0
Other Property [Member] | Commercial real estate
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		0
Other Property [Member] | Loans secured by real estate
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		0
Other Property [Member] | Agricultural loans
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		0
Other Property [Member] | Commercial and industrial loans
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		19,000
Other Property [Member] | Consumer loans
Loans By Collateral Type [Abstract]
Financing Receivable, Individually Evaluated for Impairment		$ 11,000
Accounting Standards Update 2016-13 [Member]
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	1,672,000
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease)	1,672,000
Accounting Standards Update 2016-13 [Member] | Construction and land development
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	(113,000)
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease)	(113,000)
Accounting Standards Update 2016-13 [Member] | Agricultural real estate
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	230,000
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease)	230,000
Accounting Standards Update 2016-13 [Member] | 1-4 Family residential properties
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	756,000
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease)	756,000
Accounting Standards Update 2016-13 [Member] | Commercial Real Estate Including Multifamily
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease)	541,000
Accounting Standards Update 2016-13 [Member] | Commercial real estate
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	541,000
Accounting Standards Update 2016-13 [Member] | Agricultural loans
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	(363,000)
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease)	(363,000)
Accounting Standards Update 2016-13 [Member] | Commercial Including Other
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease)	155,000
Accounting Standards Update 2016-13 [Member] | Commercial and industrial loans
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	155,000
Accounting Standards Update 2016-13 [Member] | Consumer loans
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	466,000
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease)	466,000
Accounting Standards Update 2016-13 [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	833,000
Accounting Standards Update 2016-13 [Member] | Financial Asset Acquired with Credit Deterioration [Member] | Construction and land development
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	291,000
Accounting Standards Update 2016-13 [Member] | Financial Asset Acquired with Credit Deterioration [Member] | 1-4 Family residential properties
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	42,000
Accounting Standards Update 2016-13 [Member] | Financial Asset Acquired with Credit Deterioration [Member] | Commercial real estate
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	459,000
Accounting Standards Update 2016-13 [Member] | Financial Asset Acquired with Credit Deterioration [Member] | Commercial and industrial loans
Allowance for Loan Losses [Abstract]
Financing Receivable, Allowance for Credit Loss	$ 41,000