SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) loan item	Dec. 31, 2015 USD ($) loan	Dec. 31, 2014 USD ($) loan
Cash Flow Statements [Abstract]
Paid interest	$ 28,800,000	$ 29,000,000	$ 35,000,000
Income taxes paid	47,400,000	78,400,000	60,700,000
Unsettled purchases of securities			10,000,000
Loans foreclosed and transferred to OREO	9,800,000	7,400,000	14,700,000
Mortgage Loan Related to Property Sales	541,000	1,500,000	$ 4,400,000
Loans and Leases [Abstract]
Threshold loan amount for which a new appraisal is ordered, when characteristics of potential impairment exist	$ 500,000
Period over which an appraisal is considered current	12 months
Impaired loans	$ 38,237,000	$ 51,392,000
Specific reserves included in the allowance for credit losses	$ 4,400,000
Days past due of principal or interest at which loans and leases may be placed in non-accrual status	90 days
Minimum sustained period of repayment performance for TDR loans to return to accrual status	6 months
Loans held for sale [Abstract]
Number of mortgage loans repurchased | loan	25	24	21
Amount of mortgage loans repurchased	$ 1,600,000	$ 2,000,000
Losses recognized related to repurchased and make whole loans	451,000	442,000	$ 913,000
Amount reserved for potential losses from representation and warranty obligations	$ 1,700,000
Percentage of remaining principal balance of delinquent loans that may be repurchased by the servicer (in hundredths)	100.00%
Amount of loans subject to buy back	$ 22,300,000
Derivative Instruments [Abstract]
Notional amount	$ 213,600,000	$ 255,600,000
Average maturity	30 months 6 days	42 months 3 days
Average interest receive rate (in hundredths)	2.90%	2.60%
Average interest pay rate (in hundredths)	5.60%	5.60%
Stock-Based Compensation [Abstract]
Number of stock-based employee compensation plans | item	3
Basic Plan [Member]
Pension and Postretirement Benefits Accounting [Abstract]
Discount rate assumptions for determination of projected benefit obligation (in hundredths)	4.10%	4.44%
Restoration Plan [Member]
Pension and Postretirement Benefits Accounting [Abstract]
Discount rate assumptions for determination of projected benefit obligation (in hundredths)	3.94%	4.20%
Supplemental Plan [Member]
Pension and Postretirement Benefits Accounting [Abstract]
Discount rate assumptions for determination of projected benefit obligation (in hundredths)	3.35%	3.40%