Income taxes - Reconciliation of Income Taxes Computed at the United States Federal Statutory Tax Rates to the Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Federal taxes calculated at statutory rate, amount	$ 51,041	$ 17,317	$ 23,003
Amount increase (decrease) resulting from:
State taxes, net of federal benefit	8,788	3,197	4,792
(Benefit) expense from equity based compensation	(2,719)	153	(1,353)
Municipal interest income, net of interest disallowance	(1,818)	(1,507)	(908)
Bank-owned life insurance	(324)	(327)	(51)
NOL Carryback provision under CARES Act	(3,424)	0	0
Merger and offering costs	123	289	66
Section 162(m) limitation	1,381	0	0
Other	(298)	(290)	176
Total	$ 52,750	$ 18,832	$ 25,725
Federal taxes calculated at statutory rate, percent	21.00%	21.00%	21.00%
Percentage increase (decrease) resulting from:
State taxes, net of federal benefit	3.50%	3.80%	4.40%
(Benefit) expense from equity based compensation	(1.10%)	0.20%	(1.20%)
Municipal interest income, net of interest disallowance	(0.80%)	(1.80%)	(0.80%)
Bank-owned life insurance	(0.10%)	(0.40%)	(0.10%)
NOL Carryback provision under CARES Act	(1.40%)	0.00%	0.00%
Merger and offering costs	0.10%	0.40%	0.10%
Section 162(m) limitation	0.60%	0.00%	0.00%
Other	(0.10%)	(0.40%)	0.10%
Total	21.70%	22.80%	23.50%