Condensed Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Interest and Dividend Income, Operating [Abstract]
Interest and fees on loans and leases	$ 196,521	$ 235,949	$ 412,708	$ 464,713
Taxable interest and dividends on investments	50,069	50,634	102,691	102,510
Non-taxable interest on investment securities	5,501	5,529	10,987	10,931
Loans held for sale	184	145	359	293
Total interest income	252,275	292,257	526,745	578,447
Interest Expense [Abstract]
Deposits	18,805	32,757	46,648	63,777
Securities sold under agreements to repurchase and other borrowings	980	3,904	4,710	6,656
Federal Home Loan Bank advances	3,748	7,772	10,617	15,557
Long-term debt	4,335	6,037	9,562	9,119
Total interest expense	27,868	50,470	71,537	95,109
Net interest income	224,407	241,787	455,208	483,338
Provision for credit losses	40,003	11,900	116,088	20,500
Net interest income after provision for credit losses	184,407	229,887	339,208	462,838
Noninterest Income [Abstract]
Deposit service fees	35,839	43,118	78,409	86,142
Loan and lease related fees	6,968	6,558	13,464	14,377
Wealth and investment services	7,102	8,309	15,841	15,960
Mortgage banking activities	4,205	932	7,098	1,696
Increase in cash surrender value of life insurance policies	3,624	3,650	7,204	7,234
Gain on Sale of Investments	0	0	8	0
Other income	2,338	13,286	11,430	19,056
Total non-interest income	60,076	75,853	133,454	144,465
Noninterest Expense [Abstract]
Compensation and benefits	99,731	98,527	201,618	196,312
Occupancy	14,245	14,019	28,730	28,715
Technology and equipment	27,468	25,767	55,305	51,464
Intangible assets amortization	962	962	1,924	1,924
Marketing	3,286	4,243	6,788	7,571
Professional and outside services	6,158	5,634	11,821	11,682
Deposit insurance	5,015	4,453	9,740	8,883
Other expense	19,719	27,035	39,494	49,775
Total non-interest expense	176,584	180,640	355,420	356,326
Income before income tax expense	67,899	125,100	117,242	250,977
Income tax expense	14,802	26,451	25,946	52,592
Net income	53,097	98,649	91,296	198,385
Preferred stock dividends and other	(2,368)	(2,456)	(4,530)	(4,902)
Earnings applicable to common shareholders	$ 50,729	$ 96,193	$ 86,766	$ 193,483
Earnings Per Share, Basic and Diluted [Abstract]
Basic	$ 0.57	$ 1.05	$ 0.96	$ 2.11
Diluted	$ 0.57	$ 1.05	$ 0.96	$ 2.11
Provision for credit losses	$ 40,000	$ 11,900	$ 116,000	$ 20,500