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EMPLOYEE RETIREMENT PLANS AND POSTRETIREMENT BENEFITS - Fair Value of Plan Assets by Category (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of Plan Assets | $ 17,293 | $ 14,903 | $ 13,433
Fair Value, Inputs, Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of Plan Assets | 15,189 | 13,704 |
Fair Value, Inputs, Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of Plan Assets | 1,109 | 1,045 |
Fair Value, Inputs, Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of Plan Assets | 995 | 154 |
Multi-asset Fund [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of Plan Assets | $ 5,149 | 4,825 |
Investment percentage within Plan Asset category | 29.80% |  |
Multi-asset Fund [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of Plan Assets | $ 5,149 | 4,825 |
Diversified Growth Fund [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of Plan Assets | $ 5,134 | 4,855 |
Investment percentage within Plan Asset category | 29.70% |  |
Diversified Growth Fund [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of Plan Assets | $ 5,134 | 4,855 |
Index-Linked Gilts [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of Plan Assets |  | 1,934 |
Index-Linked Gilts [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of Plan Assets |  | 1,934 |
Corporate Bonds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of Plan Assets | $ 4,906 | 2,090 |
Investment percentage within Plan Asset category | 28.40% |  |
Corporate Bonds [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of Plan Assets | $ 4,906 | 2,090 |
Insurance Contract [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of Plan Assets | $ 1,109 | 1,045 |
Investment percentage within Plan Asset category | 6.40% |  |
Insurance Contract [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of Plan Assets | $ 1,109 | 1,045 |
Defined Benefit Plan, Cash [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of Plan Assets | 995 | 154 |
Defined Benefit Plan, Cash [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair value of Plan Assets | $ 995 | $ 154 |

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