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LONG-TERM OBLIGATIONS (Details) - USD ($) $ in Thousands	1 Months Ended	6 Months Ended
LONG-TERM OBLIGATIONS (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Line of Credit Facility [Line Items]
Cash and temporary investments		$ 53,934	$ 57,521	$ 37,116	$ 26,072
First Tennessee Bank National Association \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving credit facility		50,000
Line of credit outstanding borrowings		$ 0	$ 0
Proceeds from Lines of Credit	$ 25,000
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%