Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest Income:
Interest and fees on loans and leases	$ 708,566	$ 621,028	$ 552,441
Taxable interest and dividends on securities	181,131	180,346	190,061
Non-taxable interest on securities	22,874	19,090	15,948
Loans held for sale	1,034	1,449	1,590
Interest Expense:
Deposits	62,253	49,858	46,031
Securities sold under agreements to repurchase and other borrowings	14,365	14,528	16,861
Federal Home Loan Bank advances	30,320	29,033	22,858
Long-term debt	10,380	9,981	9,665
Total interest expense	117,318	103,400	95,415
Total interest income	913,605	821,913	760,040
Net interest income	796,287	718,513	664,625
Provision for loan and lease losses	40,900	56,350	49,300
Net interest income (loss) after provision for loan and lease losses	755,387	662,163	615,325
Non-interest Income:
Deposit service fees	151,137	140,685	135,057
Loan and lease related fees	26,448	26,581	25,594
Wealth and investment services	31,055	28,962	32,486
Mortgage banking activities	9,937	14,635	7,795
Increase in cash surrender value of life insurance policies	14,627	14,759	13,020
Gain on sale of investment securities, net	0	414	609
Impairment loss on securities recognized in earnings	(126)	(149)	(110)
Other income	26,400	38,591	23,326
Total non-interest income	259,478	264,478	237,777
Non-interest Expense:
Compensation and benefits	359,926	332,127	297,517
Occupancy	60,490	61,110	48,836
Technology and equipment	89,464	79,882	80,813
Intangible assets amortization	4,062	5,652	6,340
Marketing	17,421	19,703	16,053
Professional and outside services	16,858	14,801	11,156
Deposit insurance	25,649	26,006	24,042
Other expense	87,205	83,910	70,584
Total non-interest expense	661,075	623,191	555,341
Income before income tax expense	353,790	303,450	297,761
Income tax expense	98,351	96,323	93,032
Net income	255,439	207,127	204,729
Preferred stock dividends and other	(8,608)	(8,704)	(9,368)
Earnings applicable to common shareholders	$ 246,831	$ 198,423	$ 195,361
Earnings per common share:
Earnings per common share, Basic (in dollars per share)	$ 2.68	$ 2.17	$ 2.15
Earnings per common share, Diluted (in dollars per share)	$ 2.67	$ 2.16	$ 2.13