Consolidated Statements of Earnings (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
INTEREST INCOME:
Interest and fees on loans	$ 49,105	$ 41,311	$ 95,851	$ 80,894
Interest on investment securities:
Taxable	12,719	8,343	24,073	15,774
Exempt from federal income tax	9,983	11,408	20,324	22,900
Interest on federal funds sold and interest-bearing deposits in banks	271	120	912	397
Total interest income	72,078	61,182	141,160	119,965
INTEREST EXPENSE:
Interest on deposits	4,005	1,930	7,524	3,520
Other	462	167	576	340
Total interest expense	4,467	2,097	8,100	3,860
Net interest income	67,611	59,085	133,060	116,105
PROVISION FOR LOAN LOSSES	1,105	1,725	2,415	3,675
Net interest income after provision for loan losses	66,506	57,360	130,645	112,430
NONINTEREST INCOME:
ATM, interchange and credit card fees	7,041	6,598	14,037	12,762
Net gain on sale of available-for-sale securities (includes $67 and $747 for the three months ended June 30, 2018 and 2017, respectively, and $1,288 and $750 for the six months ended June 30, 2018 and 2017, respectively, related to accumulated other comprehensive earnings reclassifications)	67	747	1,288	750
Net gain (loss) on sale of foreclosed assets	19	(72)	118	(31)
Net gain (loss) on sale of assets		(200)	(91)	(196)
Interest on loan recoveries	289	337	408	491
Other	1,676	942	3,034	1,877
Total noninterest income	25,488	23,170	49,912	44,455
NONINTEREST EXPENSE:
Salaries and employee benefits	26,862	23,465	53,065	46,724
Net occupancy expense	2,806	2,771	5,689	5,370
Equipment expense	3,440	3,665	6,957	7,102
FDIC insurance premiums	632	550	1,199	1,097
ATM, interchange and credit card expenses	2,205	1,803	4,348	3,516
Professional and service fees	2,026	2,025	4,439	3,842
Printing, stationery and supplies	612	536	1,098	974
Operational and other losses	305	574	871	1,559
Software amortization and expense	479	995	1,003	1,495
Amortization of intangible assets	384	165	771	333
Other	7,393	7,226	15,503	13,914
Total noninterest expense	47,144	43,775	94,943	85,926
EARNINGS BEFORE INCOME TAXES	44,850	36,755	85,614	70,959
INCOME TAX EXPENSE (includes $14 and $261 for the three months ended June 30, 2018 and 2017, respectively, and $270 and $263 for the six months ended June 30, 2018 and 2017, respectively, related to income tax expense from reclassification items)	7,217	8,500	13,462	16,105
NET EARNINGS	$ 37,633	$ 28,255	$ 72,152	$ 54,854
EARNINGS PER SHARE, BASIC	$ 0.56	$ 0.43	$ 1.07	$ 0.83
EARNINGS PER SHARE, ASSUMING DILUTION	0.55	0.43	1.06	0.83
DIVIDENDS PER SHARE	$ 0.21	$ 0.19	$ 0.40	$ 0.37
Trust Fees [Member]
NONINTEREST INCOME:
Revenue from contract with customer	$ 7,070	$ 5,747	$ 13,975	$ 11,764
Service Charges on Deposit Accounts [Member]
NONINTEREST INCOME:
Revenue from contract with customer	5,375	4,883	10,259	9,433
Real Estate Mortgage Operations [Member]
NONINTEREST INCOME:
Revenue from contract with customer	$ 3,951	$ 4,188	$ 6,884	$ 7,605