Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Interest income:
Loans, including fees	$ 674,611	$ 680,064	$ 741,747
Securities:
Taxable	89,550	93,569	117,082
Tax-exempt	226,683	233,614	233,842
Interest-bearing deposits	17,878	12,893	35,590
Federal funds sold	31	723	5,260
Resell agreements	16	172	264
Total interest income	1,008,769	1,021,035	1,133,785
Interest expense:
Deposits	14,520	32,018	99,742
Federal funds purchased	32	100	347
Repurchase agreements	2,209	4,382	19,328
Junior subordinated deferrable interest debentures	2,484	3,560	5,706
Subordinated notes	4,657	4,656	4,657
Federal Home Loan Bank advances	0	318	0
Total interest expense	23,902	45,034	129,780
Net interest income	984,867	976,001	1,004,005
Credit loss expense	63	241,230	33,759
Net interest income after credit loss expense	984,804	734,771	970,246
Non-interest income:
Trust and investment management fees	148,994	129,272	126,722
Service charges on deposit accounts	83,292	80,873	88,983
Insurance commissions and fees	51,548	50,313	52,345
Interchange and card transaction fees	17,461	13,470	14,873
Other charges, commissions and fees	36,836	34,825	37,123
Net gain (loss) on securities transactions	69	108,989	293
Other	48,528	47,712	43,563
Total non-interest income	386,728	465,454	363,902
Non-interest expense:
Salaries and wages	395,497	387,328	375,029
Employee benefits	82,029	75,676	86,230
Net occupancy	107,344	102,938	89,466
Technology, furniture and equipment	112,738	105,232	91,995
Deposit insurance	12,232	10,502	10,126
Intangible amortization	697	918	1,168
Other	171,457	166,310	180,665
Total non-interest expense	881,994	848,904	834,679
Income before income taxes	489,538	351,321	499,469
Income taxes	46,459	20,170	55,870
Net income	443,079	331,151	443,599
Preferred stock dividends	7,157	2,016	8,063
Redemption of preferred stock	0	5,514	0
Net income available to common shareholders	$ 435,922	$ 323,621	$ 435,536
Earnings per common share:
Basic (in dollars per share)	$ 6.79	$ 5.11	$ 6.89
Diluted (in dollars per share)	$ 6.76	$ 5.10	$ 6.84