Securities - Rollforward by major security type (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Schedule of Held-to-maturity Securities [Line Items]
Shareholder's equity	$ 577,807	$ 574,807	$ 571,441	$ 576,708	$ 395,346	$ 388,108	$ 378,516	$ 367,466
Provision (credit) for credit loss	3
Debt Securities, Held-to-maturity, Allowance for Credit Loss, Ending Balance	55
ASU 2016-03 - Topic 326
Schedule of Held-to-maturity Securities [Line Items]
Shareholder's equity	58
Adjustment
Schedule of Held-to-maturity Securities [Line Items]
Shareholder's equity				(6,062)
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
Shareholder's equity				$ 2,359