SEGMENT REPORTING (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Net interest revenue	$ 112,316	$ 107,309	$ 223,475	$ 213,382
Provision for credit losses	2,000	(5,000)	3,000	(10,000)	$ (13,000)
Net interest revenue, after provision for credit losses	110,316	112,309	220,475	223,382
Noninterest revenue	69,683	74,314	135,198	147,629
Noninterest expense	128,718	128,177	271,018	265,110
Income before income taxes	51,281	58,446	84,655	105,901
Income tax expense (benefit)	16,589	18,733	27,414	33,922
Net income	34,692	39,713	57,241	71,979
Total assets at end of period	14,137,160	13,634,931	14,137,160	13,634,931	$ 13,798,662
Depreciation and amortization	7,169	7,749	14,355	15,504
Operating Segments [Member] | Community Banking [Member]
Net interest revenue	102,890	97,679	204,351	194,518
Provision for credit losses	985	(5,831)	2,104	(9,798)
Net interest revenue, after provision for credit losses	101,905	103,510	202,247	204,316
Noninterest revenue	20,734	20,224	41,043	40,617
Noninterest expense	75,162	74,749	164,203	159,211
Income before income taxes	47,477	48,985	79,087	85,722
Income tax expense (benefit)	16,078	16,295	26,956	27,904
Net income	31,399	32,690	52,131	57,818
Total assets at end of period	10,271,318	9,868,018	10,271,318	9,868,018
Depreciation and amortization	5,280	5,577	10,542	11,089
Operating Segments [Member] | Insurance Agencies [Member]
Net interest revenue	16	35	35	67
Net interest revenue, after provision for credit losses	16	35	35	67
Noninterest revenue	28,543	29,280	61,908	62,478
Noninterest expense	24,781	25,296	50,263	50,612
Income before income taxes	3,778	4,019	11,680	11,933
Income tax expense (benefit)	1,511	1,609	4,651	4,755
Net income	2,267	2,410	7,029	7,178
Total assets at end of period	219,280	211,142	219,280	211,142
Depreciation and amortization	1,034	1,232	2,094	2,497
Operating Segments [Member] | General Corporate And Other [Member]
Net interest revenue	9,410	9,595	19,089	18,797
Provision for credit losses	1,015	831	896	(202)
Net interest revenue, after provision for credit losses	8,395	8,764	18,193	18,999
Noninterest revenue	20,406	24,810	32,247	44,534
Noninterest expense	28,775	28,132	56,552	55,287
Income before income taxes	26	5,442	(6,112)	8,246
Income tax expense (benefit)	(1,000)	829	(4,193)	1,263
Net income	1,026	4,613	(1,919)	6,983
Total assets at end of period	3,646,562	3,555,771	3,646,562	3,555,771
Depreciation and amortization	$ 855	$ 940	$ 1,719	$ 1,918