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FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Debt (Details) $ in Thousands | Mar. 31, 2021 USD ($) | Dec. 31, 2020 USD ($)
--- | --- | ---
Carrying Value |  |
Fair value disclosure |  |
Financial instruments | $ 288,080 | $ 305,623
Fair Value |  |
Fair value disclosure |  |
Financial instruments | 294,643 | 312,749
Credit Facility | Carrying Value | Level 2 |  |
Fair value disclosure |  |
Financial instruments | 70,000 | 70,000
Credit Facility | Fair Value | Level 2 |  |
Fair value disclosure |  |
Financial instruments | 70,000 | 70,000
Notes payable | Carrying Value | Level 2 |  |
Fair value disclosure |  |
Financial instruments | 196,830 | 214,216
Notes payable | Fair Value | Level 2 |  |
Fair value disclosure |  |
Financial instruments | $ 201,282 | $ 217,226
New England Pension Fund withdrawal liability | Discount Rate |  |
Fair value disclosure |  |
Measurement input | 0.034 | 0.026
New England Pension Fund withdrawal liability | Carrying Value | Level 2 |  |
Fair value disclosure |  |
Financial instruments | $ 21,250 | $ 21,407
New England Pension Fund withdrawal liability | Fair Value | Level 2 |  |
Fair value disclosure |  |
Financial instruments | $ 23,361 | $ 25,523

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