Loans and Allowance for Loan and Lease Losses - Summary of loans by portfolio type and internal credit quality ratings (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator
Gross loans	$ 1,369,747	$ 1,126,339
Pass:
Financing Receivable, Credit Quality Indicator
Gross loans	1,262,371	1,061,030
Special Mention:
Financing Receivable, Credit Quality Indicator
Gross loans	24,935	28,281
Substandard:
Financing Receivable, Credit Quality Indicator
Gross loans	78,615	37,028
Doubtful:
Financing Receivable, Credit Quality Indicator
Gross loans	3,826	0
Commercial loans
Financing Receivable, Credit Quality Indicator
Gross loans	698,280	409,420
Commercial loans | Pass:
Financing Receivable, Credit Quality Indicator
Gross loans	623,600	357,079
Commercial loans | Special Mention:
Financing Receivable, Credit Quality Indicator
Gross loans	20,321	21,894
Commercial loans | Substandard:
Financing Receivable, Credit Quality Indicator
Gross loans	50,532	30,447
Commercial loans | Doubtful:
Financing Receivable, Credit Quality Indicator
Gross loans	3,826	0
Commercial real estate loans – owner occupied
Financing Receivable, Credit Quality Indicator
Gross loans	195,379	219,483
Commercial real estate loans – owner occupied | Pass:
Financing Receivable, Credit Quality Indicator
Gross loans	163,675	206,589
Commercial real estate loans – owner occupied | Special Mention:
Financing Receivable, Credit Quality Indicator
Gross loans	4,239	6,387
Commercial real estate loans – owner occupied | Substandard:
Financing Receivable, Credit Quality Indicator
Gross loans	27,465	6,507
Commercial real estate loans – all other
Financing Receivable, Credit Quality Indicator
Gross loans	203,330	208,283
Commercial real estate loans – all other | Pass:
Financing Receivable, Credit Quality Indicator
Gross loans	203,330	208,283
Residential mortgage loans – multi-family
Financing Receivable, Credit Quality Indicator
Gross loans	164,575	176,523
Residential mortgage loans – multi-family | Pass:
Financing Receivable, Credit Quality Indicator
Gross loans	164,201	176,523
Residential mortgage loans – multi-family | Special Mention:
Financing Receivable, Credit Quality Indicator
Gross loans	375	0
Residential mortgage loans – single family
Financing Receivable, Credit Quality Indicator
Gross loans	15,522	18,782
Residential mortgage loans – single family | Pass:
Financing Receivable, Credit Quality Indicator
Gross loans	15,522	18,782
Construction and land development loans
Financing Receivable, Credit Quality Indicator
Gross loans	7,247	2,981
Construction and land development loans | Pass:
Financing Receivable, Credit Quality Indicator
Gross loans	7,247	2,981
Consumer loans
Financing Receivable, Credit Quality Indicator
Gross loans	85,414	90,867
Consumer loans | Pass:
Financing Receivable, Credit Quality Indicator
Gross loans	84,796	90,793
Consumer loans | Substandard:
Financing Receivable, Credit Quality Indicator
Gross loans	$ 618	$ 74