FAIR VALUE MEASUREMENTS - Available-for-sale securities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities - Amortized Cost Basis	$ 37,689	$ 36,778
Available-for-sale Securities - Gross Unrealized Gains	140	64
Available-for-sale Securities - Gross Unrealized Losses	(88)	(57)
Available-for-sale Securities - Fair Value	37,741	36,785
Corporate Bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities - Amortized Cost Basis	26,928	26,324
Available-for-sale Securities - Gross Unrealized Gains	140	64
Available-for-sale Securities - Gross Unrealized Losses	(88)	(57)
Available-for-sale Securities - Fair Value	26,980	26,331
Panacea preferred stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities - Amortized Cost Basis	5,029	4,865
Available-for-sale Securities - Gross Unrealized Gains	0	0
Available-for-sale Securities - Gross Unrealized Losses	0	0
Available-for-sale Securities - Fair Value	5,029	4,865
Notes Receivable [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities - Amortized Cost Basis	5,732	5,589
Available-for-sale Securities - Gross Unrealized Gains	0	0
Available-for-sale Securities - Gross Unrealized Losses	0	0
Available-for-sale Securities - Fair Value	$ 5,732	$ 5,589

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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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).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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