Consolidated Statement of Earnings - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
INTEREST INCOME:
Interest and fees on loans	$ 161,018	$ 151,662	$ 136,684
Interest on investment securities:
Taxable	27,626	29,673	28,402
Exempt from federal income tax	43,302	40,080	33,081
Interest on federal funds sold and interest-bearing deposits in banks	342	208	372
Total interest income	232,288	221,623	198,539
INTEREST EXPENSE:
Interest on deposits	4,503	3,642	3,883
Other	948	446	298
Total interest expense	5,451	4,088	4,181
Net interest income	226,837	217,535	194,358
PROVISION FOR LOAN LOSSES	10,212	9,685	4,465
Net interest income after provision for loan losses	216,625	207,850	189,893
NONINTEREST INCOME:
Trust fees	19,636	19,252	18,766
Service charges on deposit accounts	18,386	17,171	16,910
ATM, interchange and credit card fees	23,910	21,860	19,427
Real estate mortgage operations	16,086	10,409	6,511
Net gain (loss) on sale of available-for-sale securities (includes $1,270, $432 and ($4) for the years ended December 31, 2016, 2015 and 2014, respectively, related to accumulated comprehensive earnings reclassifications)	1,270	432	(4)
Net gain on sale of foreclosed assets	456	538	904
Net gain (loss) on sale of assets	168	(820)	10
Interest on loan recoveries	2,112	1,050	601
Other	3,108	3,540	3,499
Total noninterest income	85,132	73,432	66,624
NONINTEREST EXPENSE:
Salaries and employee benefits	90,739	80,999	70,456
Loss from partial settlement of pension plan	267		2,909
Net occupancy expense	10,420	10,314	9,100
Equipment expense	13,479	12,222	10,740
FDIC insurance premiums	2,680	3,153	2,725
ATM, interchange and credit card expenses	7,231	6,384	6,870
Professional and service fees	6,877	4,831	4,295
Printing, stationery and supplies	2,093	2,278	2,637
Amortization of intangible assets	738	561	275
Other	31,306	28,722	27,918
Total noninterest expense	165,830	149,464	137,925
EARNINGS BEFORE INCOME TAXES	135,927	131,818	118,592
INCOME TAX EXPENSE (includes $445, $151 and ($1) for the years ended December 31, 2016, 2015 and 2014, respectively, related to income tax expense from reclassification items)	31,153	31,437	29,033
NET EARNINGS	$ 104,774	$ 100,381	$ 89,559
NET EARNINGS PER SHARE, BASIC	$ 1.59	$ 1.55	$ 1.40
NET EARNINGS PER SHARE, ASSUMING DILUTION	$ 1.59	$ 1.54	$ 1.39