Fair Value of Assets and Liabilities, Part II (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Mortgage Servicing Rights (MSR) Impairment (Recovery)	$ 268,000
Foreclosed Assets Held for Sale [Abstract]
Other real estate owned	2,784,000		$ 3,644,000
Financial Assets [Abstract]
Available-for-sale securities	617,801,000		686,048,000
Debt Securities, Held-to-maturity	24,563,000		69,542,000
Debt Securities, Held-to-maturity, Fair Value	24,806,000		69,572,000
Operating lease right-of-use assets	16,542,000		17,006,000
Financial Liabilities [Abstract]
Operating lease liabilities	16,568,000		17,007,000
Carrying Amount [Member]
Financial Assets [Abstract]
Cash and due from banks	181,100,000		84,154,000
Federal funds sold	927,000		926,000
Certificates of deposit investments	4,380,000		4,625,000
Available-for-sale securities	617,801,000		686,048,000
Debt Securities, Held-to-maturity	24,563,000		69,542,000
Loans held for sale	1,251,000		1,820,000
Loans net of allowance for loan losses	2,710,171,000		2,666,616,000
Interest receivable	15,422,000		15,577,000
Federal Reserve Bank stock	9,401,000		9,401,000
Federal Home Loan Bank stock	5,450,000		4,105,000
Financial Liabilities [Abstract]
Deposits	2,908,627,000		2,917,366,000
Securities sold under agreements to repurchase	231,649,000		208,109,000
Interest payable	2,029,000		2,261,000
Federal Home Loan Bank borrowings	119,921,000		113,895,000
Other borrowings	5,000,000		5,000,000
Junior subordinated debentures	18,900,000		18,858,000
Fair Value [Member]
Financial Assets [Abstract]
Cash and due from banks	181,100,000		84,154,000
Federal funds sold	927,000		926,000
Certificates of deposit investments	4,380,000		4,625,000
Available-for-sale securities	617,801,000		686,048,000
Debt Securities, Held-to-maturity, Fair Value	24,806,000		69,572,000
Loans held for sale	1,251,000		1,820,000
Loans net of allowance for loan losses	2,627,881,000		2,622,053,000
Interest receivable	15,422,000		15,577,000
Federal Reserve Bank stock	9,401,000		9,401,000
Federal Home Loan Bank stock	5,450,000		4,105,000
Financial Liabilities [Abstract]
Deposits	2,920,736,000		2,924,144,000
Securities sold under agreements to repurchase	231,699,000		208,016,000
Interest payable	2,029,000		2,261,000
Federal Home Loan Bank borrowings	124,463,000		114,510,000
Other borrowings	5,000,000		5,000,000
Junior subordinated debentures	14,632,000		15,596,000
Fair Value, Nonrecurring [Member] | Carrying Amount [Member]
Foreclosed Assets Held for Sale [Abstract]
Other real estate owned	2,784,000
Fair Value, Nonrecurring [Member] | Fair Value [Member]
Foreclosed Assets Held for Sale [Abstract]
Other real estate owned	160,000
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial Assets [Abstract]
Cash and due from banks	181,100,000		84,154,000
Federal funds sold	927,000		926,000
Available-for-sale securities	146,000		219,000
Debt Securities, Held-to-maturity, Fair Value	0		0
Loans held for sale	0		0
Loans net of allowance for loan losses	0		0
Interest receivable	0		0
Federal Reserve Bank stock	0		0
Federal Home Loan Bank stock	0		0
Financial Liabilities [Abstract]
Deposits	0		0
Securities sold under agreements to repurchase	0		0
Interest payable	0		0
Federal Home Loan Bank borrowings	0		0
Other borrowings	0		5,000,000
Junior subordinated debentures	0		0
Significant Other Observable Inputs (Level 2)
Financial Assets [Abstract]
Cash and due from banks	0		0
Federal funds sold	0		0
Certificates of deposit investments	4,380,000		4,625,000
Available-for-sale securities	616,865,000		684,856,000
Debt Securities, Held-to-maturity, Fair Value	24,806,000		69,572,000
Loans held for sale	1,251,000		1,820,000
Loans net of allowance for loan losses	0		0
Interest receivable	15,422,000		15,577,000
Federal Reserve Bank stock	9,401,000		9,401,000
Federal Home Loan Bank stock	5,450,000		4,105,000
Financial Liabilities [Abstract]
Deposits	2,353,150,000		2,332,866,000
Securities sold under agreements to repurchase	231,699,000		208,016,000
Interest payable	2,029,000		2,261,000
Federal Home Loan Bank borrowings	124,463,000		114,510,000
Other borrowings	5,000,000		0
Junior subordinated debentures	14,632,000		15,596,000
Significant Unobservable Inputs (Level 3)
Financial Assets [Abstract]
Cash and due from banks	0		0
Federal funds sold	0		0
Available-for-sale securities	790,000		973,000
Debt Securities, Held-to-maturity, Fair Value	0		0
Loans held for sale	0		0
Loans net of allowance for loan losses	2,627,881,000		2,622,053,000
Interest receivable	0		0
Federal Reserve Bank stock	0		0
Federal Home Loan Bank stock	0		0
Financial Liabilities [Abstract]
Deposits	567,586,000		591,278,000
Securities sold under agreements to repurchase	0		0
Interest payable	0		0
Federal Home Loan Bank borrowings	0		0
Other borrowings	0		0
Junior subordinated debentures	0		0
Impaired loans (collateral dependent) | Fair Value, Nonrecurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	9,514,000		12,727,000
Impaired loans (collateral dependent) | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Nonrecurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	0		0
Impaired loans (collateral dependent) | Significant Other Observable Inputs (Level 2) | Fair Value, Nonrecurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	$ 0		$ 0
Impaired loans (collateral dependent) | Significant Unobservable Inputs (Level 3) | Minimum [Member] | Third Party Valuations [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Discount to reflect realizable value	0.00%		0.00%
Impaired loans (collateral dependent) | Significant Unobservable Inputs (Level 3) | Maximum [Member] | Third Party Valuations [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Discount to reflect realizable value	40.00%		40.00%
Impaired loans (collateral dependent) | Significant Unobservable Inputs (Level 3) | Weighted Average [Member] | Third Party Valuations [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Discount to reflect realizable value	20.00%		20.00%
Impaired loans (collateral dependent) | Significant Unobservable Inputs (Level 3) | Fair Value, Nonrecurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	$ 9,514,000		$ 12,727,000
Assets Held-for-sale [Member] | Fair Value, Nonrecurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	160,000		935,000
Assets Held-for-sale [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Nonrecurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	0		0
Assets Held-for-sale [Member] | Significant Other Observable Inputs (Level 2) | Fair Value, Nonrecurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	$ 0		$ 0
Assets Held-for-sale [Member] | Significant Unobservable Inputs (Level 3) | Minimum [Member] | Third Party Valuations [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Discount to reflect realizable value less estimated selling costs (in hundredths)	0.00%		0.00%
Assets Held-for-sale [Member] | Significant Unobservable Inputs (Level 3) | Maximum [Member] | Third Party Valuations [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Discount to reflect realizable value less estimated selling costs (in hundredths)	40.00%		40.00%
Assets Held-for-sale [Member] | Significant Unobservable Inputs (Level 3) | Weighted Average [Member] | Third Party Valuations [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Discount to reflect realizable value less estimated selling costs (in hundredths)	35.00%		35.00%
Assets Held-for-sale [Member] | Significant Unobservable Inputs (Level 3) | Fair Value, Nonrecurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	$ 160,000		$ 935,000
Mortgage Servicing Rights [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Mortgage Servicing Rights (MSR) Impairment (Recovery)	18,000	$ 0	(380,000)
Finite-Lived Intangible Assets, Net	1,296,000	$ 2,043,000	1,444,000	$ 2,101,000
Mortgage Servicing Rights [Member] | Fair Value, Nonrecurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Finite-Lived Intangible Assets, Net	1,296,000		1,444,000
Indefinite-Lived Contractual Rights	1,564,000
Mortgage Servicing Rights [Member] | Significant Other Observable Inputs (Level 2) | Fair Value, Nonrecurring [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Finite-Lived Intangible Assets, Net	$ 0		$ 0
Mortgage Servicing Rights [Member] | Significant Unobservable Inputs (Level 3) | Minimum [Member] | Third Party Valuations [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Discount to reflect realizable value	9.00%		9.50%
Mortgage Servicing Rights [Member] | Significant Unobservable Inputs (Level 3) | Maximum [Member] | Third Party Valuations [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Discount to reflect realizable value	11.00%		12.50%
Mortgage Servicing Rights [Member] | Significant Unobservable Inputs (Level 3) | Weighted Average [Member] | Third Party Valuations [Member]
Assets Measured On Recurring And Nonrecurring Basis Valuation Techniques [Abstract]
Discount to reflect realizable value	9.10%		9.70%