| FAIR VALUE MEASUREMENTS - Estimated Fair Value Of Other Financial Assets And Liabilities (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended | |||
|---|---|---|---|---|---|
| Jun. 30, 2019 | Mar. 31, 2019 | Sep. 30, 2019 | Sep. 30, 2018 | Dec. 31, 2018 | |
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |||||
| Long-term debt, including current portion | $ 160,576 | $ 162,275 | |||
| Purchase of investments | $ 5,000 | 5,000 | $ 0 | ||
| Cash proceeds from sale of investment | $ 4,400 | 4,430 | $ 0 | ||
| Net loss on sale of investments | $ 600 | ||||
| Level 1 | |||||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |||||
| Long-term debt, including current portion | 0 | 0 | |||
| Level 2 | |||||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |||||
| Long-term debt, including current portion | 168,920 | 159,367 | |||
| Level 3 | |||||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | |||||
| Long-term debt, including current portion | $ 0 | $ 0 | |||
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- Definition Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Amount of unrealized and realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). No definition available. 
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
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- Definition Amount of cash outflow to acquire investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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