Loans and allowance for credit losses - Changes in Allowance for Credit Losses by Class of Financing Receivable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 170,389	$ 31,139	$ 28,932
Provision for credit losses	(38,995)	94,606	7,053
Recoveries of loans previously charged-off	2,033	3,003	1,106
Loans charged off	(7,868)	(15,305)	(5,952)
Initial allowance on loans purchased with deteriorated credit quality		25,500
Balance at end of period	125,559	170,389	31,139
Cumulative effect adjustment to adopt ASC 326 | Non-purchased credit deteriorated
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		30,888
Balance at end of period			30,888
Cumulative effect adjustment to adopt ASC 326 | Purchased credit impaired
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		558
Balance at end of period			558
Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	14,748	4,805	5,348
Provision for credit losses	4,178	13,830	2,251
Recoveries of loans previously charged-off	861	1,712	136
Loans charged off	(4,036)	(11,735)	(2,930)
Initial allowance on loans purchased with deteriorated credit quality		754
Balance at end of period	15,751	14,748	4,805
Commercial and industrial | Cumulative effect adjustment to adopt ASC 326 | Non-purchased credit deteriorated
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		5,300
Balance at end of period			5,300
Commercial and industrial | Cumulative effect adjustment to adopt ASC 326 | Purchased credit impaired
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		82
Balance at end of period			82
Construction
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	58,477	10,194	9,729
Provision for credit losses	(29,874)	40,807	454
Recoveries of loans previously charged-off	3	205	11
Loans charged off	(30)	(18)	0
Initial allowance on loans purchased with deteriorated credit quality		5,606
Balance at end of period	28,576	58,477	10,194
Construction | Cumulative effect adjustment to adopt ASC 326 | Non-purchased credit deteriorated
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		1,533
Balance at end of period			1,533
Construction | Cumulative effect adjustment to adopt ASC 326 | Purchased credit impaired
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		150
Balance at end of period			150
Residential real estate | 1-to-4 family mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	19,220	3,112	3,428
Provision for credit losses	(87)	6,408	(175)
Recoveries of loans previously charged-off	125	122	79
Loans charged off	(154)	(403)	(220)
Initial allowance on loans purchased with deteriorated credit quality		1,640
Balance at end of period	19,104	19,220	3,112
Residential real estate | 1-to-4 family mortgage | Cumulative effect adjustment to adopt ASC 326 | Non-purchased credit deteriorated
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		7,920
Balance at end of period			7,920
Residential real estate | 1-to-4 family mortgage | Cumulative effect adjustment to adopt ASC 326 | Purchased credit impaired
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		421
Balance at end of period			421
Residential real estate | Residential line of credit
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	10,534	752	811
Provision for credit losses	(4,728)	5,649	112
Recoveries of loans previously charged-off	115	125	138
Loans charged off	(18)	(22)	(309)
Initial allowance on loans purchased with deteriorated credit quality		572
Balance at end of period	5,903	10,534	752
Residential real estate | Residential line of credit | Cumulative effect adjustment to adopt ASC 326 | Non-purchased credit deteriorated
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		3,461
Balance at end of period			3,461
Residential real estate | Residential line of credit | Cumulative effect adjustment to adopt ASC 326 | Purchased credit impaired
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		(3)
Balance at end of period			(3)
Residential real estate | Multi-family mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	7,174	544	566
Provision for credit losses	(197)	5,506	(22)
Recoveries of loans previously charged-off	0	0	0
Loans charged off	(1)	0	0
Initial allowance on loans purchased with deteriorated credit quality		784
Balance at end of period	6,976	7,174	544
Residential real estate | Multi-family mortgage | Cumulative effect adjustment to adopt ASC 326 | Non-purchased credit deteriorated
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		340
Balance at end of period			340
Residential real estate | Multi-family mortgage | Cumulative effect adjustment to adopt ASC 326 | Purchased credit impaired
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		0
Balance at end of period			0
Commercial real estate | Owner occupied
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	4,849	4,109	3,132
Provision for credit losses	7,588	(1,739)	869
Recoveries of loans previously charged-off	156	83	108
Loans charged off	0	(304)	0
Initial allowance on loans purchased with deteriorated credit quality		659
Balance at end of period	12,593	4,849	4,109
Commercial real estate | Owner occupied | Cumulative effect adjustment to adopt ASC 326 | Non-purchased credit deteriorated
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		1,879
Balance at end of period			1,879
Commercial real estate | Owner occupied | Cumulative effect adjustment to adopt ASC 326 | Purchased credit impaired
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		162
Balance at end of period			162
Commercial real estate | Non-owner occupied
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	44,147	4,621	4,149
Provision for credit losses	(16,813)	17,789	484
Recoveries of loans previously charged-off	0	0	0
Loans charged off	(1,566)	(711)	(12)
Initial allowance on loans purchased with deteriorated credit quality		15,442
Balance at end of period	25,768	44,147	4,621
Commercial real estate | Non-owner occupied | Cumulative effect adjustment to adopt ASC 326 | Non-purchased credit deteriorated
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		6,822
Balance at end of period			6,822
Commercial real estate | Non-owner occupied | Cumulative effect adjustment to adopt ASC 326 | Purchased credit impaired
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		184
Balance at end of period			184
Consumer and other
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	11,240	3,002	1,769
Provision for credit losses	938	6,356	3,080
Recoveries of loans previously charged-off	773	756	634
Loans charged off	(2,063)	(2,112)	(2,481)
Initial allowance on loans purchased with deteriorated credit quality		43
Balance at end of period	$ 10,888	11,240	3,002
Consumer and other | Cumulative effect adjustment to adopt ASC 326 | Non-purchased credit deteriorated
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		3,633
Balance at end of period			3,633
Consumer and other | Cumulative effect adjustment to adopt ASC 326 | Purchased credit impaired
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period		$ (438)
Balance at end of period			$ (438)