GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 57,540	$ 57,253
Accumulated amortization	(40,563)	(36,359)
Net carrying amount	16,977	20,894
Estimated aggregate amortization expense [Abstract]
Oct - Dec 2016	1,275
2017	4,413
2018	3,566
2019	2,782
2020	2,119
Thereafter	2,822
Net carrying amount	16,977	20,894
Components of goodwill [Abstract]
Goodwill	469,966	468,076
Goodwill, activity	1,890
Accumulated impairment	(4,824)	(4,824)
Accumulated impairment, activity	0
Goodwill, net	465,142	463,252	$ 375,174
Goodwill, net, activity	1,890
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	39,688	39,688
Accumulated amortization	(31,975)	(29,899)
Net carrying amount	7,713	9,789
Estimated aggregate amortization expense [Abstract]
Net carrying amount	7,713	9,789
Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	17,852	17,565
Accumulated amortization	(8,588)	(6,460)
Net carrying amount	9,264	11,105
Estimated aggregate amortization expense [Abstract]
Net carrying amount	$ 9,264	$ 11,105