Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loans including fees:
Taxable	$ 389,219	$ 349,095	$ 304,452
Nontaxable	13,970	12,287	11,566
Investment securities:
Taxable	63,031	57,005	57,336
Nontaxable	28,858	28,617	25,788
Money market and other interest-earning investments	258	130	47
Total interest income	495,336	447,134	399,189
Interest Expense
Deposits	20,356	17,283	14,168
Federal funds purchased and interbank borrowings	1,966	673	265
Securities sold under agreements to repurchase	1,270	1,509	1,488
Federal Home Loan Bank advances	24,818	15,547	8,121
Other borrowings	9,758	9,419	9,031
Total interest expense	58,168	44,431	33,073
Net interest income	437,168	402,703	366,116
Provision for loan losses	3,050	960	2,923
Net interest income after provision for loan losses	434,118	401,743	363,193
Noninterest Income
Wealth management fees	37,316	34,641	34,395
Service charges on deposit accounts	41,331	41,578	43,372
Debit card and ATM fees	17,676	16,769	21,340
Mortgage banking revenue	18,449	20,240	12,540
Insurance premiums and commissions	617	20,527	42,714
Investment product fees	20,977	18,822	17,924
Capital markets income	6,544	3,227	1,082
Company-owned life insurance	8,654	8,479	8,604
Net securities gains (losses)	9,135	5,848	5,718
Recognition of deferred gain on sale leaseback transactions	2,080	16,057	16,444
Gain on sale of ONB Insurance Group, Inc.		41,864
Net gain on branch divestitures			15,627
Change in FDIC indemnification asset		233	(9,034)
Other income	20,603	24,545	19,906
Total noninterest income	183,382	252,830	230,632
Noninterest Expense
Salaries and employee benefits	246,738	252,892	243,875
Occupancy	46,511	50,947	53,239
Equipment	13,560	13,448	13,183
Marketing	13,172	14,620	10,410
Data processing	32,306	32,002	27,309
Communication	9,284	9,959	9,586
Professional fees	16,840	15,705	11,756
Loan expense	6,596	7,632	6,373
Supplies	2,406	2,865	2,275
FDIC assessment	9,480	8,681	7,503
Other real estate owned expense	3,376	4,195	2,703
Amortization of intangibles	11,841	12,486	11,746
Amortization of tax credit investments	11,733
Other expense	24,993	28,715	30,974
Total noninterest expense	448,836	454,147	430,932
Income before income taxes	168,664	200,426	162,893
Income tax expense	72,939	66,162	46,177
Net income	$ 95,725	$ 134,264	$ 116,716
Net income per common share - basic	$ 0.69	$ 1.05	$ 1.01
Net income per common share - diluted	$ 0.69	$ 1.05	$ 1.00
Weighted average number of common shares outstanding - basic	137,821	127,705	115,726
Weighted average number of common shares outstanding - diluted	138,513	128,301	116,255
Dividends per common share	$ 0.52	$ 0.52	$ 0.48