Securities - Roll-forward by major security type (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Held-to-maturity Securities [Line Items]
Shareholder's equity	$ 577,889,000	$ 576,708,000	$ 367,466,000	$ 271,239,000
Provision (credit) for credit loss	(4,000)
Debt Securities, Held-to-maturity, Allowance for Credit Loss, Ending Balance	54,000
ASU 2016-03 - Topic 326
Schedule of Held-to-maturity Securities [Line Items]
Shareholder's equity	58,000
Adjustment
Schedule of Held-to-maturity Securities [Line Items]
Shareholder's equity		(6,062,000)
Restatement Adjustment | ASU 2016-03 - Topic 326
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity, Allowance for Credit Loss, Beginning Balance	$ 58,000
Shareholder's equity		$ 2,359,000