Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest, fee and dividend income
Interest and fees on loans	$ 267,096	$ 250,994	$ 241,828
Securities available for sale	28,564	24,033	20,418
Securities held to maturity	10,934	9,852	9,233
Other	2,813	2,068	1,745
Total interest, fee and dividend income	309,407	286,947	273,224
Interest expense
Deposits	14,475	14,366	14,257
Short-term borrowings	5,996	2,309	783
Long-term debt	2,299	3,204	3,355
Junior subordinated debt	3,144	2,627	2,221
Total interest expense	25,914	22,506	20,616
Net interest income	283,493	264,441	252,608
Provision for loan losses	30,988	25,431	18,285
Net interest income after provision for loan losses	252,505	239,010	234,323
Noninterest income
Insurance and other financial services revenue	23,532	24,396	24,211
Service charges on deposit accounts	16,750	16,729	17,056
ATM and debit card fees	21,372	19,448	18,248
Retirement plan administration fees	20,213	16,063	14,146
Trust	19,586	18,565	19,026
Bank owned life insurance income	5,175	5,195	4,334
Net securities gains (losses)	1,867	(644)	3,087
Gain on the sale of equity investment	818	0	4,179
Other	11,991	15,961	14,194
Total noninterest income	121,304	115,713	118,481
Noninterest expense
Salaries and employee benefits	133,610	131,284	125,633
Occupancy	21,808	20,940	22,095
Data processing and communications	17,068	16,495	16,588
Professional fees and outside services	13,499	13,617	13,407
Equipment	15,225	14,295	13,408
Office supplies and postage	6,284	6,168	6,367
FDIC expenses	4,767	5,111	5,145
Advertising	2,744	2,556	2,654
Amortization of intangible assets	3,960	3,928	4,864
Loan collection and other real estate owned, net	4,763	3,458	2,620
Other	21,920	18,070	23,395
Total noninterest expense	245,648	235,922	236,176
Income before income tax expense	128,161	118,801	116,628
Income tax (expense) benefit	46,010	40,392	40,203
Net income	$ 82,151	$ 78,409	$ 76,425
Earnings per share
Basic (in dollars per share)	$ 1.89	$ 1.81	$ 1.74
Diluted (in dollars per share)	$ 1.87	$ 1.80	$ 1.72