Loans and Allowance for Loan and Lease Losses - Summary of loans by portfolio type and internal credit quality ratings (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator
Gross loans	$ 1,278,981	$ 1,126,339
Pass:
Financing Receivable, Credit Quality Indicator
Gross loans	1,165,395	1,061,030
Special Mention:
Financing Receivable, Credit Quality Indicator
Gross loans	29,120	28,281
Substandard:
Financing Receivable, Credit Quality Indicator
Gross loans	82,906	37,028
Doubtful:
Financing Receivable, Credit Quality Indicator
Gross loans	1,560	0
Commercial loans
Financing Receivable, Credit Quality Indicator
Gross loans	614,737	409,420
Commercial loans | Pass:
Financing Receivable, Credit Quality Indicator
Gross loans	536,255	357,079
Commercial loans | Special Mention:
Financing Receivable, Credit Quality Indicator
Gross loans	21,818	21,894
Commercial loans | Substandard:
Financing Receivable, Credit Quality Indicator
Gross loans	55,104	30,447
Commercial loans | Doubtful:
Financing Receivable, Credit Quality Indicator
Gross loans	1,560	0
Commercial real estate loans – owner occupied
Financing Receivable, Credit Quality Indicator
Gross loans	195,586	219,483
Commercial real estate loans – owner occupied | Pass:
Financing Receivable, Credit Quality Indicator
Gross loans	161,122	206,589
Commercial real estate loans – owner occupied | Special Mention:
Financing Receivable, Credit Quality Indicator
Gross loans	6,931	6,387
Commercial real estate loans – owner occupied | Substandard:
Financing Receivable, Credit Quality Indicator
Gross loans	27,532	6,507
Commercial real estate loans – all other
Financing Receivable, Credit Quality Indicator
Gross loans	199,911	208,283
Commercial real estate loans – all other | Pass:
Financing Receivable, Credit Quality Indicator
Gross loans	199,912	208,283
Residential mortgage loans – multi-family
Financing Receivable, Credit Quality Indicator
Gross loans	161,947	176,523
Residential mortgage loans – multi-family | Pass:
Financing Receivable, Credit Quality Indicator
Gross loans	161,576	176,523
Residential mortgage loans – multi-family | Special Mention:
Financing Receivable, Credit Quality Indicator
Gross loans	371	0
Residential mortgage loans – single family
Financing Receivable, Credit Quality Indicator
Gross loans	13,764	18,782
Residential mortgage loans – single family | Pass:
Financing Receivable, Credit Quality Indicator
Gross loans	13,764	18,782
Construction and land development loans
Financing Receivable, Credit Quality Indicator
Gross loans	9,300	2,981
Construction and land development loans | Pass:
Financing Receivable, Credit Quality Indicator
Gross loans	9,300	2,981
Consumer loans
Financing Receivable, Credit Quality Indicator
Gross loans	83,736	90,867
Consumer loans | Pass:
Financing Receivable, Credit Quality Indicator
Gross loans	83,466	90,793
Consumer loans | Substandard:
Financing Receivable, Credit Quality Indicator
Gross loans	$ 270	$ 74