CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
INTEREST INCOME:
Interest and fees on loans	$ 424,941	$ 424,615	$ 393,871
Interest on securities:
Taxable	98,263	73,147	54,131
Nontaxable	12,484	9,868	14,120
Interest on federal funds sold	0	4	0
Interest on interest bearing deposits in other financial institutions	924	6,695	3,698
TOTAL INTEREST INCOME	536,612	514,329	465,820
INTEREST EXPENSE:
Interest on deposits	30,287	63,734	35,667
Interest on short-term borrowings	610	1,748	1,696
Interest on other borrowings (includes $(1,820), $170, and $179 of interest expense (benefit) related to derivatives reclassified from accumulated other comprehensive income (loss) for the years ended December 31, 2020, 2019, and 2018, respectively)	13,986	15,118	14,503
TOTAL INTEREST EXPENSE	44,883	80,600	51,866
NET INTEREST INCOME	491,729	433,729	413,954
Provision for credit losses	67,066	16,657	24,013
NET INTEREST INCOME AFTER PROVISION FOR CREDIT LOSSES	424,663	417,072	389,941
NONINTEREST INCOME:
Revenue from contract with customers	71,085	75,342	71,612
Loan servicing income	2,977	4,843	7,292
Securities gains, net (includes $7,592, $7,659, and $1,085 of net security gains reclassified from accumulated other comprehensive income (loss) for the years ended December 31, 2020, 2019, and 2018, respectively)	7,793	7,659	1,085
Unrealized gain on equity securities, net	640	525	212
Net gains on sale of loans held for sale	28,515	15,555	21,450
Valuation allowance on servicing rights	(1,778)	(911)	(46)
Income on bank owned life insurance	3,554	3,785	2,793
Other noninterest income	7,505	9,410	4,762
TOTAL NONINTEREST INCOME	120,291	116,208	109,160
NONINTEREST EXPENSES:
Salaries and employee benefits	202,668	200,341	195,362
Occupancy	26,554	25,429	25,328
Furniture and equipment	12,514	12,013	11,927
Professional fees	54,068	47,697	41,414
Advertising	5,235	9,825	9,516
Core deposit intangibles and customer relationship intangibles amortization	10,670	11,972	9,355
Other real estate and loan collection expenses	1,340	1,035	3,038
(Gain) loss on sales/valuations of assets, net	5,101	(19,422)	1,845
Acquisition, integration and restructuring costs	5,381	6,580	7,564
Partnership investment in tax credit projects	3,801	8,030	4,233
Other noninterest expenses	43,631	45,661	44,306
TOTAL NONINTEREST EXPENSES	370,963	349,161	353,888
INCOME BEFORE INCOME TAXES	173,991	184,119	145,213
Income taxes (includes $2,376, $1,890, and $165 of income tax expense reclassified from accumulated other comprehensive income (loss) for the years ended December 31, 2020, 2019, and 2018, respectively)	36,053	34,990	28,215
NET INCOME	137,938	149,129	116,998
Preferred dividends	(4,451)	0	(39)
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS	$ 133,487	$ 149,129	$ 116,959
EARNINGS PER COMMON SHARE - BASIC (in dollars per share)	$ 3.58	$ 4.14	$ 3.54
EARNINGS PER COMMON SHARE - DILUTED (in dollars per share)	3.57	4.14	3.52
CASH DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 0.80	$ 0.68	$ 0.59
Service charges and fees
NONINTEREST INCOME:
Revenue from contract with customers	$ 47,467	$ 52,157	$ 48,706
Trust fees
NONINTEREST INCOME:
Revenue from contract with customers	20,862	19,399	18,393
Brokerage and insurance commissions
NONINTEREST INCOME:
Revenue from contract with customers	$ 2,756	$ 3,786	$ 4,513