SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)	12 Months Ended
	Dec. 31, 2015 USD ($) loan item	Dec. 31, 2014 USD ($) loan	Dec. 31, 2013 USD ($) loan
Cash Flow Statements [Abstract]
Paid interest	$ 29,000,000	$ 35,000,000	$ 51,900,000
Income taxes paid	78,400,000	60,700,000	39,500,000
Unsettled purchases of securities		10,000,000	1,200,000
Loans foreclosed and transferred to OREO	7,400,000	14,700,000	29,300,000
Mortgage Loan Related to Property Sales	1,500,000	4,400,000	13,700,000
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	$ 51,392,000	28,101,000
Cumulative charge-offs during the period	26,700,000	$ 25,000,000	$ 42,200,000
Specific reserves included in the allowance for credit losses	$ 2,400,000
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	24	21	16
Amount of mortgage loans repurchased	$ 2,000,000	$ 2,100,000	$ 931,000
Losses recognized related to repurchased and make whole loans	442,000	913,000	$ 661,000
Amount reserved for potential losses from representation and warranty obligations	$ 1,300,000
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	$ 22,700,000
Derivative Instruments [Abstract]
Notional amount	$ 255,600,000	$ 324,200,000
Average maturity	42 months 3 days	49 months 15 days
Average interest receive rate (in hundredths)	2.60%	2.50%
Average interest pay rate (in hundredths)	5.60%	5.60%
Stock-Based Compensation [Abstract]
Number of stock-based employee compensation plans | item	3
Impaired Loans [Member]
Loans and Leases [Abstract]
Cumulative charge-offs during the period	$ 11,400,000
Minimum [Member]
Loans and Leases [Abstract]
Marketing period	180 days
Maximum [Member]
Loans and Leases [Abstract]
Marketing period	360 days
Basic Plan [Member]
Pension and Postretirement Benefits Accounting [Abstract]
Discount rate assumptions for determination of projected benefit obligation (in hundredths)	4.44%	4.10%
Restoration Plan [Member]
Pension and Postretirement Benefits Accounting [Abstract]
Discount rate assumptions for determination of projected benefit obligation (in hundredths)	4.20%	3.90%
Supplemental Plan [Member]
Pension and Postretirement Benefits Accounting [Abstract]
Discount rate assumptions for determination of projected benefit obligation (in hundredths)	3.40%	3.10%