MARKETABLE SECURITIES - Continuous Unrealized Loss Position (Details) - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months Estimated Fair Market Value, Total marketable securities	$ 93,255,000		$ 93,255,000
Less Than 12 Months Gross Unrealized Losses, Total marketable securities	(77,000)		(77,000)
12 Months or Longer Estimated Fair Market Value, Total marketable securities	0		0
12 Months or Longer Gross Unrealized Losses, Total marketable securities	0		0
Total Estimated Fair Market Value, Total marketable securities	93,255,000		93,255,000
Total Gross Unrealized Losses, Total marketable securities	(77,000)		(77,000)
Unrealized losses on marketable securities	0	$ 0	0	$ 0
Corporate securities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months Estimated Fair Market Value, Total marketable securities	93,255,000		93,255,000
Less Than 12 Months Gross Unrealized Losses, Total marketable securities	(77,000)		(77,000)
12 Months or Longer Estimated Fair Market Value, Total marketable securities	0		0
12 Months or Longer Gross Unrealized Losses, Total marketable securities	0		0
Total Estimated Fair Market Value, Total marketable securities	93,255,000		93,255,000
Total Gross Unrealized Losses, Total marketable securities	$ (77,000)		$ (77,000)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 30
-Section 50
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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