SEGMENT REPORTING (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Results of Operations [Abstract]
Net interest revenue	$ 111,070	$ 105,613	$ 324,452	$ 310,217
Provision for credit losses	(3,000)		(13,000)
Net interest revenue, after provision for credit losses	114,070	105,613	337,452	310,217
Noninterest revenue	62,953	69,278	210,582	205,633
Noninterest expense	126,450	133,699	391,560	388,360
Income before income taxes	50,573	41,192	156,474	127,490
Income tax expense (benefit)	16,230	12,414	50,152	39,400
Net income	34,343	28,778	106,322	88,090
Selected Financial Information [Abstract]
Total assets at end of period	13,787,424	13,071,557	13,787,424	13,071,557	$ 13,326,369
Depreciation and amortization	7,454	7,895	22,956	23,668
Community Banking [Member]
Results of Operations [Abstract]
Net interest revenue	101,202	96,576	295,720	284,165
Provision for credit losses	(3,164)	(4,001)	(12,963)	(3,525)
Net interest revenue, after provision for credit losses	104,366	100,577	308,683	287,690
Noninterest revenue	21,576	24,761	62,193	71,152
Noninterest expense	73,492	87,629	232,704	244,050
Income before income taxes	52,450	37,709	138,172	114,792
Income tax expense (benefit)	17,517	11,863	45,417	36,984
Net income	34,933	25,846	92,755	77,808
Selected Financial Information [Abstract]
Total assets at end of period	10,131,502	9,575,772	10,131,502	9,575,772
Depreciation and amortization	5,417	5,545	16,558	16,836
Insurance Agencies [Member]
Results of Operations [Abstract]
Net interest revenue	35	32	84	90
Net interest revenue, after provision for credit losses	35	32	84	90
Noninterest revenue	29,280	29,053	90,801	89,545
Noninterest expense	25,296	24,930	76,110	73,616
Income before income taxes	4,019	4,155	14,775	16,019
Income tax expense (benefit)	1,609	1,677	5,923	6,402
Net income	2,410	2,478	8,852	9,617
Selected Financial Information [Abstract]
Total assets at end of period	211,536	207,612	211,536	207,612
Depreciation and amortization	1,140	1,322	3,637	3,945
General Corporate And Other [Member]
Results of Operations [Abstract]
Net interest revenue	9,833	9,005	28,648	25,962
Provision for credit losses	164	4,001	(37)	3,525
Net interest revenue, after provision for credit losses	9,669	5,004	28,685	22,437
Noninterest revenue	12,097	15,464	57,588	44,936
Noninterest expense	27,662	21,140	82,746	70,694
Income before income taxes	(5,896)	(672)	3,527	(3,321)
Income tax expense (benefit)	(2,896)	(1,126)	(1,188)	(3,986)
Net income	(3,000)	454	4,715	665
Selected Financial Information [Abstract]
Total assets at end of period	3,444,386	3,288,173	3,444,386	3,288,173
Depreciation and amortization	$ 897	$ 1,028	$ 2,761	$ 2,887