GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 146,669	$ 57,541
Accumulated amortization	(53,819)	(41,839)
Net carrying amount	92,850	15,702
Estimated aggregate amortization expense [Abstract]
Oct - Dec 2017	4,904
2018	17,259
2019	14,502
2020	12,043
2021	10,288
Thereafter	33,854
Net carrying amount	92,850	15,702
Components of goodwill [Abstract]
Goodwill	736,329	469,966
Goodwill, activity	266,363
Accumulated impairment	(4,824)	(4,824)
Accumulated impairment, activity	0
Goodwill, net	731,505	465,142	$ 465,142
Goodwill, net, activity	266,363
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	62,902	39,688
Accumulated amortization	(36,101)	(32,581)
Net carrying amount	26,801	7,107
Estimated aggregate amortization expense [Abstract]
Net carrying amount	26,801	7,107
Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	83,767	17,853
Accumulated amortization	(17,718)	(9,258)
Net carrying amount	66,049	8,595
Estimated aggregate amortization expense [Abstract]
Net carrying amount	$ 66,049	$ 8,595