Condensed Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Interest and Dividend Income, Operating [Abstract]
Interest and fees on loans and leases	$ 188,001	$ 236,453	$ 600,709	$ 701,166
Taxable interest and dividends on investments	45,549	52,046	148,240	154,556
Non-taxable interest on investment securities	5,460	5,471	16,447	16,402
Loans held for sale	229	166	588	459
Total interest income	239,239	294,136	765,984	872,583
Interest Expense [Abstract]
Deposits	12,598	34,214	59,246	97,991
Securities sold under agreements to repurchase and other borrowings	608	6,571	5,318	13,227
Federal Home Loan Bank advances	2,528	6,910	13,145	22,467
Long-term debt	4,249	5,902	13,811	15,021
Total interest expense	19,983	53,597	91,520	148,706
Net interest income	219,256	240,539	674,464	723,877
Provision for credit losses	22,750	11,300	138,750	31,800
Net interest income after provision for credit losses	196,506	229,239	535,714	692,077
Noninterest Income [Abstract]
Deposit service fees	39,278	41,410	117,687	127,552
Loan and lease related fees	6,568	8,246	20,032	22,623
Wealth and investment services	8,255	8,496	24,096	24,456
Mortgage banking activities	7,087	2,133	14,185	3,829
Increase in cash surrender value of life insurance policies	3,695	3,708	10,899	10,942
Gain on Sale of Investments	0	0	8	0
Other income	10,177	5,938	21,607	24,994
Total non-interest income	75,060	69,931	208,514	214,396
Noninterest Expense [Abstract]
Compensation and benefits	104,019	98,623	305,637	294,935
Occupancy	14,275	14,087	43,005	42,802
Technology and equipment	27,846	26,180	83,151	77,644
Intangible assets amortization	1,089	961	3,013	2,885
Marketing	3,852	4,758	10,640	12,329
Professional and outside services	9,223	5,024	21,044	16,706
Deposit insurance	4,204	4,409	13,944	13,292
Other expense	19,488	25,852	58,982	75,627
Total non-interest expense	183,996	179,894	539,416	536,220
Income before income tax expense	87,570	119,276	204,812	370,253
Income tax expense	18,289	25,411	44,235	78,003
Net income	69,281	93,865	160,577	292,250
Preferred stock dividends and other	(2,391)	(2,423)	(6,819)	(7,331)
Earnings applicable to common shareholders	$ 66,890	$ 91,442	$ 153,758	$ 284,919
Earnings Per Share, Basic and Diluted [Abstract]
Basic	$ 0.75	$ 1.00	$ 1.71	$ 3.11
Diluted	$ 0.75	$ 1.00	$ 1.70	$ 3.10