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LONG-TERM OBLIGATIONS (Details) - USD ($) $ in Thousands | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 21, 2020 | Dec. 20, 2020 | Dec. 31, 2017
Line of Credit Facility [Line Items] |  |  |  |  |  |
Cash and temporary investments | $ 57,521 | $ 26,072 | $ 27,037 |  |  | $ 21,895
First Tennessee Bank National Association | Revolving Credit Facility |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |
Revolving credit facility |  |  |  | $ 50,000 |  |
Interest expense on credit facility | 235 | 684 | $ 512 |  |  |
Line of credit outstanding borrowings | $ 0 | 4,998 |  |  |  |
Debt instrument description of non-default rate of interest | LIBOR Market Index Rate plus 1.00% or 1.25% per annum, depending on the leverage ratio |  |  |  |  |
Minimum tangible net worth required for compliance |  |  |  | $ 190,000 | $ 160,000 |
Tangible net worth | $ 271,000 |  |  |  |  |
First Tennessee Bank National Association | Revolving Credit Facility | London Interbank Offered Rate (LIBOR) [Member] |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |
Interest rate | 1.14% |  |  |  |  |
First Tennessee Bank National Association | Revolving Credit Facility | Minimum |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |
Non-usage fee for current loan agreement in annual amount percentage | 0.15% |  |  |  |  |
First Tennessee Bank National Association | Revolving Credit Facility | Minimum | London Interbank Offered Rate (LIBOR) [Member] |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |
Variable interest rate in addition to reference rate | 1.00% |  |  |  |  |
First Tennessee Bank National Association | Revolving Credit Facility | Maximum |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |
Non-usage fee for current loan agreement in annual amount percentage | 0.35% |  |  |  |  |
First Tennessee Bank National Association | Revolving Credit Facility | Maximum | London Interbank Offered Rate (LIBOR) [Member] |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |
Variable interest rate in addition to reference rate | 1.25% |  |  |  |  |
Jige International S.A. | Banque Europeenne Du Credit Mutuel |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |
Maturity date | Sep. 30, 2020 |  |  |  |  |
Unsecured debt, long-term obligations due within one year |  | $ 368 |  |  |  |

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