EMPLOYEE BENEFITS (Asset Allocation) (Details) - Pension Benefits - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 199,466	$ 164,819	$ 157,644
Actual % of total	100.00%	100.00%
Fixed maturity securities - corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 13,250	$ 10,051
Actual % of total	6.70%	6.10%
Redeemable preferred stock
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 2,929	$ 2,697
Actual % of total	1.50%	1.60%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 117,117	$ 86,586
Actual % of total	58.70%	52.50%
Core plus bond separate account fund
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 20,505	$ 20,222
Actual % of total	10.30%	12.30%
U.S. property separate account fund
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 22,114	$ 20,841
Actual % of total	11.10%	12.60%
Arbitrage fund
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 9,245	$ 8,716
Actual % of total	4.60%	5.30%
United Life annuity
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 10,855	$ 10,339
Actual % of total	5.40%	6.30%
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 3,451	$ 5,367
Actual % of total	1.70%	3.30%
Minimum | Fixed maturity securities - corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Target allocation	0.00%
Minimum | Redeemable preferred stock
Defined Benefit Plan Disclosure [Line Items]
Target allocation	0.00%
Minimum | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation	50.00%
Minimum | Core plus bond separate account fund
Defined Benefit Plan Disclosure [Line Items]
Target allocation	0.00%
Minimum | U.S. property separate account fund
Defined Benefit Plan Disclosure [Line Items]
Target allocation	0.00%
Minimum | Arbitrage fund
Defined Benefit Plan Disclosure [Line Items]
Target allocation	0.00%
Minimum | United Life annuity
Defined Benefit Plan Disclosure [Line Items]
Target allocation	5.00%
Minimum | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Target allocation	0.00%
Maximum | Fixed maturity securities - corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Target allocation	15.00%
Maximum | Redeemable preferred stock
Defined Benefit Plan Disclosure [Line Items]
Target allocation	10.00%
Maximum | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation	70.00%
Maximum | Core plus bond separate account fund
Defined Benefit Plan Disclosure [Line Items]
Target allocation	40.00%
Maximum | U.S. property separate account fund
Defined Benefit Plan Disclosure [Line Items]
Target allocation	25.00%
Maximum | Arbitrage fund
Defined Benefit Plan Disclosure [Line Items]
Target allocation	10.00%
Maximum | United Life annuity
Defined Benefit Plan Disclosure [Line Items]
Target allocation	10.00%
Maximum | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Target allocation	10.00%