Consolidated Statements of Income - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
INTEREST INCOME
Interest and fees on loans and leases	$ 865,521,000	$ 850,067,000	$ 869,433,000
Interest and dividends on investment securities:
Taxable	57,987,000	46,427,000	47,842,000
Exempt from federal income tax	8,725,000	8,828,000	9,647,000
Dividends	1,491,000	1,399,000	708,000
Interest on temporary investments and interest bearing deposits	4,380,000	3,918,000	2,236,000
Total interest income	938,104,000	910,639,000	929,866,000
INTEREST EXPENSE
Interest on deposits	45,582,000	35,240,000	29,839,000
Interest on securities sold under agreement to repurchase and federal funds purchased	475,000	132,000	173,000
Interest on term debt	14,159,000	15,005,000	14,470,000
Interest on junior subordinated debentures	18,000,000	15,674,000	13,750,000
Total interest expense	78,216,000	66,051,000	58,232,000
Net interest income	859,888,000	844,588,000	871,634,000
Provision for loan and lease losses	47,254,000	41,674,000	36,589,000
Net interest income after provision for loan and lease losses	812,634,000	802,914,000	835,045,000
NON-INTEREST INCOME
Service charges on deposits	61,469,000	61,268,000	59,740,000
Brokerage revenue	16,083,000	17,033,000	18,481,000
Residential mortgage banking revenue, net	136,276,000	157,863,000	124,722,000
Gain on sales of investment securities, net	27,000	858,000	2,922,000
Gain on loan sales, net	16,721,000	13,356,000	22,380,000
Loss on junior subordinated debentures carried at fair value	(14,727,000)	(6,323,000)	(6,306,000)
BOLI income	8,214,000	8,514,000	8,351,000
Other income	53,133,000	47,371,000	45,434,000
Total non-interest income	277,196,000	299,940,000	275,724,000
NON-INTEREST EXPENSE
Salaries and employee benefits	438,180,000	424,830,000	430,936,000
Occupancy and equipment, net	150,545,000	151,944,000	142,975,000
Communications	18,932,000	21,265,000	20,615,000
Marketing	8,918,000	10,913,000	11,419,000
Services	45,302,000	42,795,000	46,379,000
FDIC assessments	15,014,000	15,508,000	13,480,000
(Gain) loss on other real estate owned, net	(557,000)	(279,000)	1,894,000
Intangible amortization	6,756,000	8,622,000	11,225,000
Merger related expenses	9,324,000	15,313,000	45,582,000
Goodwill impairment	0	142,000	0
Other expenses	55,461,000	46,102,000	39,137,000
Total non-interest expense	747,875,000	737,155,000	763,642,000
Income before income taxes	341,955,000	365,699,000	347,127,000
Provision for income taxes	95,936,000	132,759,000	124,588,000
Net income	246,019,000	232,940,000	222,539,000
Dividends and undistributed earnings allocated to participating securities	56,000	125,000	357,000
Net earnings available to common shareholders	$ 245,963,000	$ 232,815,000	$ 222,182,000
Earnings per common share:
Basic earnings per common share (usd per share)	$ 1.12	$ 1.06	$ 1.01
Diluted earnings per common share (usd per share)	$ 1.11	$ 1.05	$ 1.01
Weighted average number of common shares outstanding:
Basic (in shares)	220,251	220,282	220,327
Diluted (in shares)	220,836	220,908	221,045