SEGMENT REPORTING (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Net interest revenue	$ 114,590	$ 111,070	$ 338,065	$ 324,452
Provision for credit losses		(3,000)	3,000	(13,000)	$ (13,000)
Net interest revenue, after provision for credit losses	114,590	114,070	335,065	337,452
Noninterest revenue	70,868	62,953	206,066	210,582
Noninterest expense	129,512	126,450	400,530	391,560
Income before income taxes	55,946	50,573	140,601	156,474
Income tax expense (benefit)	18,129	16,230	45,543	50,152
Net income	37,817	34,343	95,058	106,322
Total assets at end of period	14,611,483	13,787,424	14,611,483	13,787,424	$ 13,798,662
Depreciation and amortization	7,341	7,454	21,695	22,956
Operating Segments [Member] | Community Banking [Member]
Net interest revenue	104,939	101,202	309,290	295,720
Provision for credit losses	(2,082)	(3,164)	23	(12,963)
Net interest revenue, after provision for credit losses	107,021	104,366	309,267	308,683
Noninterest revenue	20,745	21,576	61,788	62,193
Noninterest expense	76,914	73,492	241,117	232,704
Income before income taxes	50,852	52,450	129,938	138,172
Income tax expense (benefit)	17,050	17,517	43,998	45,417
Net income	33,802	34,933	85,940	92,755
Total assets at end of period	10,790,604	10,131,502	10,790,604	10,131,502
Depreciation and amortization	5,431	5,417	15,972	16,558
Operating Segments [Member] | Insurance Agencies [Member]
Net interest revenue	11	35	45	84
Net interest revenue, after provision for credit losses	11	35	45	84
Noninterest revenue	27,913	29,280	89,821	90,801
Noninterest expense	25,335	25,296	75,598	76,110
Income before income taxes	2,589	4,019	14,268	14,775
Income tax expense (benefit)	1,051	1,609	5,702	5,923
Net income	1,538	2,410	8,566	8,852
Total assets at end of period	217,062	211,536	217,062	211,536
Depreciation and amortization	1,075	1,140	3,169	3,637
Operating Segments [Member] | General Corporate And Other [Member]
Net interest revenue	9,640	9,833	28,730	28,648
Provision for credit losses	2,082	164	2,977	(37)
Net interest revenue, after provision for credit losses	7,558	9,669	25,753	28,685
Noninterest revenue	22,210	12,097	54,457	57,588
Noninterest expense	27,263	27,662	83,815	82,746
Income before income taxes	2,505	(5,896)	(3,605)	3,527
Income tax expense (benefit)	28	(2,896)	(4,157)	(1,188)
Net income	2,477	(3,000)	552	4,715
Total assets at end of period	3,603,817	3,444,386	3,603,817	3,444,386
Depreciation and amortization	$ 835	$ 897	$ 2,554	$ 2,761