Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest Income
Loans, including fees	$ 603,961	$ 543,385	$ 524,060
Investment securities:
Taxable	47,028	44,975	45,279
Tax-exempt	11,566	9,662	7,879
Dividends	369	571	985
Loans held for sale	876	728	801
Other interest income	5,066	3,779	4,785
Total Interest Income	668,866	603,100	583,789
Interest Expense
Deposits	57,791	44,693	40,482
Short-term borrowings	2,779	855	372
Long-term debt	32,932	36,780	42,941
Total Interest Expense	93,502	82,328	83,795
Net Interest Income	575,364	520,772	499,994
Provision for credit losses	23,305	13,182	2,250
Net Interest Income After Provision for Credit Losses	552,059	507,590	497,744
Non-Interest Income
Other service charges and fees	52,859	51,473	43,992
Service charges on deposit accounts	51,006	51,346	50,097
Investment management and trust services	49,249	45,270	44,056
Mortgage banking income	19,928	19,415	18,208
Other	25,861	20,124	16,420
Non-interest income before investment securities gains	198,903	187,628	172,773
Investment securities gains, net	9,071	2,550	9,066
Total Non-Interest Income	207,974	190,178	181,839
Non-Interest Expense
Salaries and employee benefits	290,130	283,353	260,832
Net occupancy expense	49,708	47,611	47,777
Other outside services	27,501	23,883	27,785
Equipment expense	38,735	36,919	34,640
Amortization of tax credit investments	11,028	0	0
Marketing	12,935	12,788	14,514
Loss on redemption of trust preferred securities	12,688	11,004	11,244
FDIC insurance expense	11,049	9,767	11,470
Marketing	8,034	7,044	7,324
State taxes	10,051	6,405	7,297
Loss on redemption of trust preferred securities	0	0	5,626
Other Noninterest Expense	53,720	50,745	51,651
Total Non-Interest Expense	525,579	489,519	480,160
Income Before Income Taxes	234,454	208,249	199,423
Income taxes	62,701	46,624	49,921
Net Income	$ 171,753	$ 161,625	$ 149,502
PER COMMON SHARE:
Net Income (Basic) (usd per share)	$ 0.98	$ 0.93	$ 0.85
Net Income (Diluted) (usd per share)	0.98	0.93	0.85
Cash Dividends (usd per share)	$ 0.47	$ 0.41	$ 0.38