EMPLOYEE BENEFITS (Fair Value of Plan Assets) (Details) - Pension Benefits - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	$ 128,430	$ 106,600	$ 102,800
Fixed maturity securities - corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	9,451	6,894
Redeemable preferred stock
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	3,144	3,744
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	69,770	58,613
Core plus bond separate account fund
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	10,401	6,605
U.S. property separate account fund
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	14,330	11,252
U.S. property separate account fund | Level 3
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	14,330	11,252	$ 9,895
Arbitrage fund
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	8,292	7,856
Recurring
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	119,047	97,583
Recurring | Level 1
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	76,573	64,976
Recurring | Level 2
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	28,144	21,355
Recurring | Level 3
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	14,330	11,252
Recurring | Fixed maturity securities - corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	9,451	6,894
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	9,451	6,894
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	3,144	3,744
Recurring | Redeemable preferred stock | Level 1
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	3,144	3,744
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	69,770	58,613
Recurring | Equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	69,770	58,613
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	10,401	6,605
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	10,401	6,605
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	14,330	11,252
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	14,330	11,252
Recurring | Arbitrage fund
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	8,292	7,856
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	8,292	7,856
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	3,659	2,619
Recurring | Money market funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Assets measured at fair value	3,659	2,619
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