Consolidated Statements of Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
INTEREST INCOME
Loans		$ 585,957	$ 637,845	$ 559,351
Securities:
Taxable interest		105,701	106,053	83,333
Tax-exempt interest		99,820	90,064	74,411
Total securities income		205,521	196,117	157,744
Federal funds and resell agreements		11,840	13,843	4,808
Interest-bearing due from banks		3,744	12,882	7,910
Trading securities		1,427	2,205	2,148
Total interest income		808,489	862,892	731,961
INTEREST EXPENSE
Deposits		58,214	154,192	92,101
Federal funds and repurchase agreements		11,787	32,553	24,737
Other		7,259	5,242	4,677
Total interest expense		77,260	191,987	121,515
Net interest income		731,229	670,905	610,446
Provision for credit losses	[1]	130,500	32,850	70,750
Net interest income after provision for credit losses		600,729	638,055	539,696
NONINTEREST INCOME
Trust and securities processing		194,646	176,913	172,163
Trading and investment banking		32,945	23,466	15,584
Service charges on deposit accounts		83,879	82,748	84,287
Insurance fees and commissions		1,369	1,634	1,292
Brokerage fees		24,350	31,261	25,807
Bankcard fees		60,544	66,727	68,520
Investment securities gains, net		120,634	2,245	3,521
Other		41,799	41,776	30,524
Total noninterest income		560,166	426,770	401,698
NONINTEREST EXPENSE
Salaries and employee benefits		495,464	461,445	419,091
Occupancy, net		47,476	47,771	45,239
Equipment		85,719	79,086	75,184
Supplies and services		15,537	18,699	16,103
Marketing and business development		14,679	26,257	24,372
Processing fees		54,213	52,198	46,977
Legal and consulting		29,765	31,504	29,859
Bankcard		18,954	17,750	17,514
Amortization of other intangible assets		6,517	5,506	5,764
Regulatory fees		10,279	11,489	12,695
Other		43,402	27,155	25,002
Total noninterest expense		822,005	778,860	717,800
Income before income taxes		338,890	285,965	223,594
Income tax expense		52,388	42,365	27,334
Income from continuing operations		286,502	243,600	196,260
Discontinued Operations
Loss from discontinued operations before taxes				(917)
Income tax benefit				(170)
Loss from discontinued operations				(747)
NET INCOME		$ 286,502	$ 243,600	$ 195,513
Basic:
Income from continuing operations		$ 5.95	$ 4.99	$ 3.98
Loss from discontinued operations				(0.01)
Net income – basic		5.95	4.99	3.97
Diluted:
Income from continuing operations		5.93	4.96	3.94
Loss from discontinued operations				(0.01)
Net income – diluted		5.93	4.96	3.93
Dividends		$ 1.25	$ 1.21	$ 1.17
Weighted average shares outstanding – basic		48,137,791	48,779,263	49,334,937
Weighted average shares outstanding – diluted		48,343,750	49,089,877	49,770,737

[1] For the years ended December 31, 2019 and 2018, this line represents the Provision for loan losses. See further discussion of this change in Note 2, “New Accounting Pronouncements.”