GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 57,541	$ 57,253
Accumulated amortization	(41,839)	(36,359)
Net carrying amount	15,702	20,894
Finite-lived intangible assets, future amortization expense [Abstract]
2017	4,413
2018	3,566
2019	2,782
2020	2,119
2021	1,531
Thereafter	1,291
Net carrying amount	15,702	20,894
Components of goodwill [Abstract]
Goodwill	469,966	468,076	$ 379,998
Goodwill, activity	1,890	88,078
Accumulated impairment	(4,824)	(4,824)	(4,824)
Accumulated impairment, activity	0	0
Goodwill, net	465,142	463,252	$ 375,174
Goodwill, net, activity	1,890	88,078
Servicing Asset at Fair Value, Amount [Roll Forward]
Carrying value before valuation allowance at beginning of period	1,472	1,089
Additions	481	403
Oneida acquisition	0	389
Amortization	(518)	(409)
Carrying value before valuation allowance at end of period	1,435	1,472
Valuation allowance balance at beginning of period	0	0
Impairment charges	(226)	(133)
Impairment recoveries	226	133
Valuation allowance balance at end of period	0	0
Net carrying value at end of period	1,435	1,472
Fair value of MSRs at end of period	1,928	1,962
Principal balance of loans sold during the year	45,852	35,491
Principal balance of loans serviced for others	365,374	377,909
Custodial escrow balances maintained in connection with loans serviced for others	$ 5,603	$ 5,700
Key economic assumptions used to estimate the value of the MSRs [Abstract]
Weighted-average contractual life	20 years 9 months 18 days	19 years 10 months 24 days
Weighted-average constant prepayment rate (CPR)	15.10%	14.90%
Weighted-average discount rate	3.50%	3.30%
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 39,688	$ 39,688
Accumulated amortization	(32,581)	(29,899)
Net carrying amount	7,107	9,789
Finite-lived intangible assets, future amortization expense [Abstract]
Net carrying amount	7,107	9,789
Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	17,853	17,565
Accumulated amortization	(9,258)	(6,460)
Net carrying amount	8,595	11,105
Finite-lived intangible assets, future amortization expense [Abstract]
Net carrying amount	$ 8,595	$ 11,105