Accounting Policies (Details) - USD ($)	Mar. 31, 2021	Jan. 01, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for loan losses	$ 65,849,000		$ 52,388,000	$ 24,498,000	$ 21,398,000
Shareholders' equity	(876,853,000)		(893,421,000)	(862,198,000)	(852,401,000)
Accrued interest receivable on held to maturity debt securities	1,120,000
Allowance for credit losses on available-for-sale portfolio	0
Accrued interest receivable on available for sale debt securities	3,340,000
Accrued interest on loans	14,200,000
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Shareholders' equity	(483,944,000)		(478,489,000)	$ (430,709,000)	$ (417,764,000)
Unfunded Loan Commitment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for loan losses	$ 8,086,000		582,000
Cumulative Effect, Period Of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for loan losses		$ 14,600,000	14,575,000
Shareholders' equity			17,051,000
Cumulative Effect, Period Of Adoption, Adjustment | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Shareholders' equity		17,100,000	17,051,000
Cumulative Effect, Period Of Adoption, Adjustment | Unfunded Loan Commitment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for loan losses		7,500,000	$ 7,504,000
Cumulative Effect, Period Of Adoption, Adjustment | PCI Loans
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for loan losses		$ 100,000