EMPLOYEE BENEFITS (Fair Value of Plan Assets) (Details) - Pension Benefits - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	$ 164,819	$ 157,644	$ 128,430
Fixed maturity securities - corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	10,051	11,003
Redeemable preferred stock
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	2,697	3,216
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	86,586	87,603
Core plus bond separate account fund
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	20,222	17,948
U.S. property separate account fund
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	20,841	15,502
U.S. property separate account fund | Level 3
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	20,841	15,502	$ 14,330
Arbitrage fund
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	8,716	8,506
Recurring
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	154,477	147,789
Recurring | Level 1
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	94,647	94,830
Recurring | Level 2
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	38,989	37,457
Recurring | Level 3
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	20,841	15,502
Recurring | Fixed maturity securities - corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	10,051	11,003
Recurring | Fixed maturity securities - corporate bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	0	0
Recurring | Fixed maturity securities - corporate bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	10,051	11,003
Recurring | Fixed maturity securities - corporate bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	0	0
Recurring | Redeemable preferred stock
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	2,697	3,216
Recurring | Redeemable preferred stock | Level 1
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	2,697	3,216
Recurring | Redeemable preferred stock | Level 2
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	0	0
Recurring | Redeemable preferred stock | Level 3
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	0	0
Recurring | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	86,586	87,603
Recurring | Equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	86,586	87,603
Recurring | Equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	0	0
Recurring | Equity securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	0	0
Recurring | Core plus bond separate account fund
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	20,222	17,948
Recurring | Core plus bond separate account fund | Level 1
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	0	0
Recurring | Core plus bond separate account fund | Level 2
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	20,222	17,948
Recurring | Core plus bond separate account fund | Level 3
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	0	0
Recurring | U.S. property separate account fund
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	20,841	15,502
Recurring | U.S. property separate account fund | Level 1
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	0	0
Recurring | U.S. property separate account fund | Level 2
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	0	0
Recurring | U.S. property separate account fund | Level 3
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	20,841	15,502
Recurring | Arbitrage fund
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	8,716	8,506
Recurring | Arbitrage fund | Level 1
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	0	0
Recurring | Arbitrage fund | Level 2
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	8,716	8,506
Recurring | Arbitrage fund | Level 3
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	0	0
Recurring | Money market funds
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	5,364	4,011
Recurring | Money market funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	5,364	4,011
Recurring | Money market funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	0	0
Recurring | Money market funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	$ 0	$ 0