Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Interest income
Loans and leases	$ 323,023	$ 325,548
Investment securities interest and dividend income	30,852	39,493
Overnight investments	1,448	4,518
Total interest income	355,323	369,559
Interest expense
Deposits	8,793	24,194
Securities sold under customer repurchase agreements	338	442
Federal Home Loan Bank borrowings	2,087	2,984
Subordinated debt	4,188	2,755
Interest Expense, Other	265	784
Total interest expense	15,671	31,159
Net interest income	339,652	338,400
Provision (credit) for loan and lease losses	(10,974)	28,355
Net interest income after provision for loan and lease losses	350,626	310,045
Noninterest income
Other service charges and fees	8,489	7,792
Insurance commissions	16,011	(51,408)
Realized gains on investment securities available for sale, net	9,207	19,795
Other	1,860	625
Total noninterest income	136,649	64,011
Noninterest expense
Salaries and wages	147,830	145,255
Employee benefits	35,725	38,511
Occupancy expense	29,743	27,480
Equipment expense	29,803	27,850
Processing fees paid to third parties	13,673	10,372
FDIC insurance expense	3,218	3,466
Collection and foreclosure-related expenses	2,198	4,054
Merger-related expenses	6,819	4,232
Other	26,917	38,751
Total noninterest expense	295,926	299,971
Income before income taxes	191,349	74,085
Income taxes	44,033	16,916
Net income	147,316	57,169
Preferred stock dividends	4,636	0
Net income available to common shareholders	$ 142,680	$ 57,169
Average shares outstanding (in shares)	9,816,405	10,473,119
Net income per share	$ 14.53	$ 5.46
Service charges on deposit accounts
Noninterest income
Revenue from contract with customers	$ 19,960	$ 18,160
Cardholder services, net
Noninterest income
Revenue from contract with customers	8,917	5,888
Mortgage income
Noninterest income
Revenue from contract with customers	32,198	26,412
Merchant services, net
Noninterest income
Revenue from contract with customers	21,536	26,413
ATM income
Noninterest income
Revenue from contract with customers	12,991	5,224
Realized gains on investment securities available for sale, net
Noninterest income
Revenue from contract with customers	3,998	3,688
Gain on extinguishment of debt
Noninterest income
Revenue from contract with customers	$ 1,482	$ 1,422