Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest income:
Loans, including fees	$ 741,747	$ 669,002	$ 534,804
Securities:
Taxable	117,082	86,370	92,979
Tax-exempt	233,842	233,358	222,620
Interest-bearing deposits	35,590	56,968	41,608
Federal funds sold and resell agreements	5,524	5,500	936
Total interest income	1,133,785	1,051,198	892,947
Interest expense:
Deposits	99,742	75,337	17,188
Federal funds purchased and repurchase agreements	19,675	8,021	1,522
Junior subordinated deferrable interest debentures	5,706	5,291	3,955
Other long-term borrowings	4,657	4,657	3,860
Total interest expense	129,780	93,306	26,525
Net interest income	1,004,005	957,892	866,422
Provision for loan losses	33,759	21,613	35,460
Net interest income after provision for loan losses	970,246	936,279	830,962
Non-interest income:
Trust and investment management fees	126,722	119,391	110,675
Service charges on deposit accounts	88,983	85,186	84,182
Insurance commissions and fees	52,345	48,967	46,169
Interchange and debit card transaction fees	14,873	13,877	23,232
Other charges, commissions and fees	37,123	37,231	39,931
Net gain (loss) on securities transactions	293	(156)	(4,941)
Other	43,563	46,790	37,222
Total non-interest income	363,902	351,286	336,470
Non-interest expense:
Salaries and wages	375,029	350,312	337,068
Employee benefits	86,230	77,323	74,575
Net occupancy	89,466	76,788	75,971
Technology, furniture and equipment	91,995	83,102	74,335
Deposit insurance	10,126	16,397	20,128
Intangible amortization	1,168	1,424	1,703
Other	180,665	173,538	175,289
Total non-interest expense	834,679	778,884	759,069
Income before income taxes	499,469	508,681	408,363
Income taxes	55,870	53,763	44,214
Net income	443,599	454,918	364,149
Preferred stock dividends	8,063	8,063	8,063
Net income available to common shareholders	$ 435,536	$ 446,855	$ 356,086
Earnings per common share:
Basic (in dollars per share)	$ 6.89	$ 6.97	$ 5.56
Diluted (in dollars per share)	$ 6.84	$ 6.90	$ 5.51