Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Interest income
Loans and leases	$ 324,288	$ 326,099	$ 647,311	$ 651,647
Investment securities interest and dividend income	35,432	36,605	66,284	76,098
Overnight investments	2,105	553	3,553	5,071
Total interest income	361,825	363,257	717,148	732,816
Interest expense
Deposits	8,542	17,916	17,335	42,110
Securities sold under customer repurchase agreements	356	399	694	841
Federal Home Loan Bank borrowings	2,099	2,472	4,186	5,456
Subordinated debt	4,181	4,677	8,369	7,432
Interest Expense, Other	254	399	519	1,183
Total interest expense	15,432	25,863	31,103	57,022
Net interest income	346,393	337,394	686,045	675,794
Provision (credit) for loan and lease losses	(19,603)	20,552	(30,577)	48,907
Net interest income after provision for loan and lease losses	365,996	316,842	716,622	626,887
Noninterest income
Other service charges and fees	8,959	7,145	17,448	14,937
Insurance commissions	11,654	64,570	27,665	13,162
Realized gains on investment securities available for sale, net	15,830	13,752	25,037	33,547
Other	1,864	2,697	3,724	3,322
Total noninterest income	134,150	165,402	270,799	229,413
Noninterest expense
Salaries and wages	153,643	146,633	301,473	291,888
Employee benefits	35,298	30,364	71,023	68,875
Occupancy expense	28,439	29,556	58,182	57,036
Equipment expense	28,902	28,774	58,705	56,624
Processing fees paid to third parties	14,427	10,186	28,100	20,558
FDIC insurance expense	3,382	3,731	6,600	7,197
Collection and foreclosure-related expenses	173	3,949	2,371	8,003
Merger-related expenses	5,769	4,369	12,588	8,601
Other	31,545	34,117	58,462	72,868
Total noninterest expense	301,578	291,679	597,504	591,650
Income before income taxes	198,568	190,565	389,917	264,650
Income taxes	45,780	36,779	89,813	53,695
Net income	152,788	153,786	300,104	210,955
Preferred stock dividends	4,636	4,790	9,272	4,790
Net income available to common shareholders	$ 148,152	$ 148,996	$ 290,832	$ 206,165
Average shares outstanding (in shares)	9,816,405	10,105,520	9,816,405	10,289,320
Net income per share	$ 15.09	$ 14.74	$ 29.63	$ 20.04
Service charges on deposit accounts
Noninterest income
Revenue from contract with customers	$ 22,471	$ 17,587	$ 42,431	$ 35,747
Cardholder services, net
Noninterest income
Revenue from contract with customers	8,532	5,363	17,449	11,251
Mortgage income
Noninterest income
Revenue from contract with customers	31,753	22,371	63,951	48,783
Merchant services, net
Noninterest income
Revenue from contract with customers	21,883	17,522	43,419	43,935
ATM income
Noninterest income
Revenue from contract with customers	5,929	9,811	18,920	15,035
Realized gains on investment securities available for sale, net
Noninterest income
Revenue from contract with customers	3,704	3,189	7,702	6,877
Gain on extinguishment of debt
Noninterest income
Revenue from contract with customers	$ 1,571	$ 1,395	$ 3,053	$ 2,817