GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 57,541	$ 57,253
Accumulated amortization	(37,802)	(36,359)
Net carrying amount	19,739	20,894
Estimated aggregate amortization expense [Abstract]
Apr - Dec 2016	4,037
2017	4,412
2018	3,566
2019	2,782
2020	2,119
Thereafter	2,823
Net carrying amount	19,739	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	(30,619)	(29,899)
Net carrying amount	9,069	9,789
Estimated aggregate amortization expense [Abstract]
Net carrying amount	9,069	9,789
Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	17,853	17,565
Accumulated amortization	(7,183)	(6,460)
Net carrying amount	10,670	11,105
Estimated aggregate amortization expense [Abstract]
Net carrying amount	$ 10,670	$ 11,105