SEGMENT REPORTING (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Results of Operations [Abstract]
Net interest revenue	$ 111,159	$ 106,073
Provision for credit losses	1,000	(5,000)	$ (13,000)
Net interest revenue, after provision for credit losses	110,159	111,073
Noninterest revenue	65,515	73,315
Noninterest expense	142,300	136,933
Income before income taxes	33,374	47,455
Income tax expense (benefit)	10,825	15,189
Net income	22,549	32,266
Selected Financial Information [Abstract]
Total assets at end of period	13,926,398	13,630,322	$ 13,798,662
Operating Segments [Member]
Results of Operations [Abstract]
Net interest revenue	111,159	106,073
Provision for credit losses	1,000	(5,000)
Net interest revenue, after provision for credit losses	110,159	111,073
Noninterest revenue	65,515	73,315
Noninterest expense	142,300	136,933
Income before income taxes	33,374	47,455
Income tax expense (benefit)	10,825	15,189
Net income	22,549	32,266
Selected Financial Information [Abstract]
Total assets at end of period	13,926,398	13,630,322
Depreciation and amortization	7,187	7,753
Operating Segments [Member] | Community Banking [Member]
Results of Operations [Abstract]
Net interest revenue	101,461	96,838
Provision for credit losses	1,119	(3,967)
Net interest revenue, after provision for credit losses	100,342	100,805
Noninterest revenue	20,309	20,393
Noninterest expense	89,041	84,462
Income before income taxes	31,610	36,736
Income tax expense (benefit)	10,802	11,607
Net income	20,808	25,129
Selected Financial Information [Abstract]
Total assets at end of period	10,136,464	9,926,741
Depreciation and amortization	5,261	5,564
Operating Segments [Member] | Insurance Agencies [Member]
Results of Operations [Abstract]
Net interest revenue	19	32
Net interest revenue, after provision for credit losses	19	32
Noninterest revenue	33,364	33,198
Noninterest expense	25,482	25,316
Income before income taxes	7,901	7,914
Income tax expense (benefit)	3,140	3,146
Net income	4,761	4,768
Selected Financial Information [Abstract]
Total assets at end of period	210,535	209,434
Depreciation and amortization	1,060	1,265
Operating Segments [Member] | General Corporate And Other [Member]
Results of Operations [Abstract]
Net interest revenue	9,679	9,203
Provision for credit losses	(119)	(1,033)
Net interest revenue, after provision for credit losses	9,798	10,236
Noninterest revenue	11,842	19,724
Noninterest expense	27,777	27,155
Income before income taxes	(6,137)	2,805
Income tax expense (benefit)	(3,117)	436
Net income	(3,020)	2,369
Selected Financial Information [Abstract]
Total assets at end of period	3,579,399	3,494,147
Depreciation and amortization	$ 866	$ 924