Loans and Allowance for Loan and Lease Losses - Schedule of composition of loan portfolio (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable
Gross loans	$ 1,369,747		$ 1,126,339
Deferred fee (income) costs, net	(781)		4,783
Allowance for loan and lease losses	(18,166)	$ (17,520)	(13,611)	$ (11,474)	$ (11,514)	$ (13,506)
Loans, net	$ 1,350,800		$ 1,117,511
Percentage of loan portfolio	100.00%		100.00%
Commercial loans
Accounts, Notes, Loans and Financing Receivable
Gross loans	$ 698,280		$ 409,420
Allowance for loan and lease losses	$ (11,487)	(11,218)	$ (8,883)	(6,809)	(6,895)	(8,071)
Percentage of loan portfolio	51.00%		36.20%
Commercial real estate loans – owner occupied
Accounts, Notes, Loans and Financing Receivable
Gross loans	$ 195,379		$ 219,483
Percentage of loan portfolio	14.30%		19.50%
Commercial real estate loans – all other
Accounts, Notes, Loans and Financing Receivable
Gross loans	$ 203,330		$ 208,283
Percentage of loan portfolio	14.80%		18.50%
Residential mortgage loans – multi-family
Accounts, Notes, Loans and Financing Receivable
Gross loans	$ 164,575		$ 176,523
Percentage of loan portfolio	12.00%		15.70%
Residential mortgage loans – single family
Accounts, Notes, Loans and Financing Receivable
Gross loans	$ 15,522		$ 18,782
Percentage of loan portfolio	1.10%		1.70%
Construction and land development loans
Accounts, Notes, Loans and Financing Receivable
Gross loans	$ 7,247		$ 2,981
Allowance for loan and lease losses	$ (77)	$ (55)	$ (34)	$ (119)	$ (295)	$ (426)
Percentage of loan portfolio	0.50%		0.30%
Consumer loans
Accounts, Notes, Loans and Financing Receivable
Gross loans	$ 85,414		$ 90,867
Percentage of loan portfolio	6.30%		8.10%