Loans, Allowance for Credit Losses - Loans, and Credit Quality - Summary of allowance for loan losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			$ 13,972	$ 13,153	$ 13,153
Provision for credit losses	$ 3,000	$ 400	9,000	900	1,200
Charge-offs			(1,002)	(629)	(927)
Recoveries			133	196	546
Net (charge-offs) recoveries			(869)	(433)	(381)
Ending balance	$ 31,388	$ 13,620	31,388	$ 13,620	13,972
Adoption of CECL
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			8,488
Ending balance					8,488
Initial PCD ACL
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			797
Ending balance					797
Cumulative Effect, Period of Adoption, Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance			$ 9,285
Ending balance					$ 9,285