Income Taxes - Differences between provision for income taxes and amount computed as statutory rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Differences between the provision for income taxes and statutory federal income tax rate
Income tax expense on pretax income at statutory rates	$ 73,030	$ 43,983	$ 50,130
Add (deduct):
State taxes, net of federal benefit	9,188	5,928	7,168
BOLI earnings	(745)	(1,052)	(1,127)
Adjustment to reserve for uncertain tax positions	153	(1,212)	84
Tax-exempt interest revenue	(2,520)	(2,169)	(1,827)
Equity compensation	(891)	(174)	(375)
Transaction costs	117	217	16
Tax credit investments	(598)	(930)	(464)
Other	228	765	(614)
Total income tax expense	$ 77,962	$ 45,356	$ 52,991