Consolidated Statements of Income - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loans including fees:
Taxable	$ 349,095,000	$ 304,452,000	$ 296,141,000
Nontaxable	12,287,000	11,566,000	10,207,000
Investment securities:
Taxable	57,005,000	57,336,000	60,903,000
Nontaxable	28,617,000	25,788,000	22,436,000
Money market and other interest-earning investments	130,000	47,000	42,000
Total interest income	447,134,000	399,189,000	389,729,000
Interest Expense
Deposits	17,283,000	14,168,000	13,326,000
Federal funds purchased and interbank borrowings	673,000	265,000	136,000
Securities sold under agreements to repurchase	1,509,000	1,488,000	1,434,000
Federal Home Loan Bank advances	15,547,000	8,121,000	4,275,000
Other borrowings	9,419,000	9,031,000	4,188,000
Total interest expense	44,431,000	33,073,000	23,359,000
Net interest income	402,703,000	366,116,000	366,370,000
Provision for loan losses	960,000	2,923,000	3,097,000
Net interest income after provision for loan losses	401,743,000	363,193,000	363,273,000
Noninterest Income
Wealth management fees	34,641,000	34,395,000	28,737,000
Service charges on deposit accounts	41,578,000	43,372,000	47,433,000
Debit card and ATM fees	16,769,000	21,340,000	25,835,000
Mortgage banking revenue	20,240,000	12,540,000	6,017,000
Insurance premiums and commissions	20,527,000	42,714,000	41,466,000
Investment product fees	18,822,000	17,924,000	17,136,000
Company-owned life insurance	8,479,000	8,604,000	6,924,000
Net securities gains	5,848,000	5,718,000	9,830,000
Total other-than-temporary impairment losses	0	0	(100,000)
Loss recognized in other comprehensive income	0	0	0
Impairment losses recognized in earnings			(100,000)
Recognition of deferred gain on sale leaseback transactions	16,057,000	16,444,000	6,094,000
Gain on sale of ONB Insurance Group, Inc.	41,864,000
Net gain on branch divestitures		15,627,000
Change in FDIC indemnification asset	233,000	(9,034,000)	(43,162,000)
Other income	27,772,000	20,988,000	18,919,000
Total noninterest income	252,830,000	230,632,000	165,129,000
Noninterest Expense
Salaries and employee benefits	252,892,000	243,875,000	219,301,000
Occupancy	50,947,000	53,239,000	49,099,000
Equipment	13,448,000	13,183,000	12,453,000
Marketing	14,620,000	10,410,000	9,591,000
Data processing	32,002,000	27,309,000	25,382,000
Communication	9,959,000	9,586,000	10,476,000
Professional fees	15,705,000	11,756,000	16,390,000
Loan expense	7,632,000	6,373,000	6,107,000
Supplies	2,865,000	2,275,000	2,958,000
FDIC assessment	8,681,000	7,503,000	6,261,000
Other real estate owned expense	4,195,000	2,703,000	3,101,000
Amortization of intangibles	12,486,000	11,746,000	9,120,000
Other expense	28,715,000	30,974,000	16,199,000
Total noninterest expense	454,147,000	430,932,000	386,438,000
Income before income taxes	200,426,000	162,893,000	141,964,000
Income tax expense	66,162,000	46,177,000	38,297,000
Net income	$ 134,264,000	$ 116,716,000	$ 103,667,000
Net income per common share - basic	$ 1.05	$ 1.01	$ 0.96
Net income per common share - diluted	$ 1.05	$ 1.00	$ 0.95
Weighted average number of common shares outstanding - basic	127,705	115,726	107,818
Weighted average number of common shares outstanding - diluted	128,301	116,255	108,365
Dividends per common share	$ 0.52	$ 0.48	$ 0.44