Loans and allowance for credit losses - Loans Outstanding by Class of Financing Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Gross loans	$ 7,604,662	$ 7,082,959
Less: Allowance for credit losses	(125,559)	(170,389)	$ (31,139)	$ (28,932)
Net loans	7,479,103	6,912,570
Paycheck Protection Program
Financing Receivable, Past Due [Line Items]
Loans originated as part of PPP program	3,990	212,645
Commercial and industrial
Financing Receivable, Past Due [Line Items]
Gross loans	1,290,565	1,346,122
Less: Allowance for credit losses	(15,751)	(14,748)	(4,805)	(5,348)
Construction
Financing Receivable, Past Due [Line Items]
Gross loans	1,327,659	1,222,220
Less: Allowance for credit losses	(28,576)	(58,477)	(10,194)	(9,729)
Residential real estate | 1-to-4 family mortgage
Financing Receivable, Past Due [Line Items]
Gross loans	1,270,467	1,089,270
Less: Allowance for credit losses	(19,104)	(19,220)	(3,112)	(3,428)
Residential real estate | Residential line of credit
Financing Receivable, Past Due [Line Items]
Gross loans	383,039	408,211
Less: Allowance for credit losses	(5,903)	(10,534)	(752)	(811)
Residential real estate | Multi-family mortgage
Financing Receivable, Past Due [Line Items]
Gross loans	326,551	175,676
Less: Allowance for credit losses	(6,976)	(7,174)	(544)	(566)
Commercial real estate | Owner occupied
Financing Receivable, Past Due [Line Items]
Gross loans	951,582	924,841
Less: Allowance for credit losses	(12,593)	(4,849)	(4,109)	(3,132)
Commercial real estate | Non-owner occupied
Financing Receivable, Past Due [Line Items]
Gross loans	1,730,165	1,598,979
Less: Allowance for credit losses	(25,768)	(44,147)	(4,621)	(4,149)
Consumer and other
Financing Receivable, Past Due [Line Items]
Gross loans	324,634	317,640
Less: Allowance for credit losses	$ (10,888)	$ (11,240)	$ (3,002)	$ (1,769)