GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 58,046	$ 45,288
Accumulated amortization	(37,152)	(33,489)
Net carrying amount	20,894	11,799
Finite-lived intangible assets, future amortization expense [Abstract]
2016	5,415
2017	4,357
2018	3,518
2019	2,742
2020	2,087
Thereafter	2,775
Net carrying amount	20,894	11,799
Components of goodwill [Abstract]
Goodwill	468,076	379,998	$ 379,815
Goodwill, activity	88,078	183
Accumulated impairment	(4,824)	(4,824)	(4,824)
Accumulated impairment, activity	0	0
Goodwill, net	463,252	375,174	$ 374,991
Goodwill, net, activity	88,078	183
Servicing Asset at Fair Value, Amount [Roll Forward]
Carrying value before valuation allowance at beginning of period	1,089	1,218
Additions	403	315
Oneida acquisition	389	0
Amortization	(409)	(444)
Carrying value before valuation allowance at end of period	1,472	1,089
Valuation allowance balance at beginning of period	0	0
Impairment charges	(133)	0
Impairment recoveries	133	0
Valuation allowance balance at end of period	0	0
Net carrying value at end of period	1,472	1,089
Fair value of MSRs at end of period	1,962	1,616
Principal balance of loans sold during the year	35,491	25,728
Principal balance of loans serviced for others	377,909	302,895
Custodial escrow balances maintained in connection with loans serviced for others	$ 5,700	$ 4,320
Key economic assumptions used to estimate the value of the MSRs [Abstract]
Weighted-average contractual life	19 years 10 months 24 days	19 years 7 months 6 days
Weighted-average constant prepayment rate (CPR)	14.90%	12.80%
Weighted-average discount rate	3.30%	3.20%
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 40,481	$ 37,911
Accumulated amortization	(30,692)	(27,888)
Net carrying amount	9,789	10,023
Finite-lived intangible assets, future amortization expense [Abstract]
Net carrying amount	9,789	10,023
Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	17,565	7,377
Accumulated amortization	(6,460)	(5,601)
Net carrying amount	11,105	1,776
Finite-lived intangible assets, future amortization expense [Abstract]
Net carrying amount	$ 11,105	$ 1,776