Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
INTEREST INCOME:
Interest and fees on loans	$ 424,615	$ 393,871	$ 304,006
Interest on securities:
Taxable	73,147	54,131	38,365
Nontaxable	9,868	14,120	19,698
Interest on federal funds sold	4	0	42
Interest on interest bearing deposits in other financial institutions	6,695	3,698	1,547
TOTAL INTEREST INCOME	514,329	465,820	363,658
INTEREST EXPENSE:
Interest on deposits	63,734	35,667	18,279
Interest on short-term borrowings	1,748	1,696	678
Interest on other borrowings (includes $170, $179, and $1,290 of interest expense related to derivatives reclassified from accumulated other comprehensive income (loss) for the years ended December 31, 2019, 2018, and 2017, respectively)	15,118	14,503	14,393
TOTAL INTEREST EXPENSE	80,600	51,866	33,350
NET INTEREST INCOME	433,729	413,954	330,308
Provision for loan losses	16,657	24,013	15,563
NET INTEREST INCOME AFTER PROVISION FOR LOAN LOSSES	417,072	389,941	314,745
NONINTEREST INCOME:
Revenue from contract with customers	75,342	71,612	59,034
Loan servicing income	4,843	7,292	5,636
Securities gains, net (includes $7,659, $1,085, and $6,764 of net security gains reclassified from accumulated other comprehensive income (loss) for the years ended December 31, 2019, 2018, and 2017, respectively)	7,659	1,085	6,973
Unrealized gain on equity securities, net	525	212	0
Net gains on sale of loans held for sale	15,555	21,450	22,251
Valuation allowance on servicing rights	(911)	(46)	21
Income on bank owned life insurance	3,785	2,793	2,772
Other noninterest income	9,410	4,762	5,335
TOTAL NONINTEREST INCOME	116,208	109,160	102,022
NONINTEREST EXPENSES:
Salaries and employee benefits	200,541	196,118	171,407
Occupancy	25,450	25,328	22,244
Furniture and equipment	12,100	12,529	11,061
Professional fees	50,022	43,510	36,474
Advertising	10,028	9,565	7,229
Core deposit intangibles and customer relationship intangibles amortization	11,972	9,355	6,077
Other real estate and loan collection expenses	1,035	3,038	2,461
(Gain) loss on sales/valuations of assets, net	(19,422)	2,208	2,475
Restructuring expenses	3,227	2,564	0
Other noninterest expenses	54,208	49,673	38,247
TOTAL NONINTEREST EXPENSES	349,161	353,888	297,675
INCOME BEFORE INCOME TAXES	184,119	145,213	119,092
Income taxes (includes $1,890, $165, and $2,042 of income tax expense reclassified from accumulated other comprehensive income (loss) for the years ended December 31, 2019, 2018, and 2017, respectively)	34,990	28,215	43,820
NET INCOME	149,129	116,998	75,272
Preferred dividends	0	(39)	(58)
Interest expense on convertible preferred debt	0	0	12
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS	$ 149,129	$ 116,959	$ 75,226
EARNINGS PER COMMON SHARE - BASIC (in dollars per share)	$ 4.14	$ 3.54	$ 2.67
EARNINGS PER COMMON SHARE - DILUTED (in dollars per share)	4.14	3.52	2.65
CASH DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 0.68	$ 0.59	$ 0.51
Service charges and fees
NONINTEREST INCOME:
Revenue from contract with customers	$ 52,157	$ 48,706	$ 39,183
Trust fees
NONINTEREST INCOME:
Revenue from contract with customers	19,399	18,393	15,818
Brokerage and insurance commissions
NONINTEREST INCOME:
Revenue from contract with customers	$ 3,786	$ 4,513	$ 4,033