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FAIR VALUE MEASUREMENTS - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
FAIR VALUE MEASUREMENTS - Narrative (Details) - USD ($)	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jul. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Contingent consideration, liability	$ 2,638,000		$ 2,638,000			$ 2,879,000
Investment income, net	2,523,000	$ 9,093,000	5,532,000	$ 23,417,000
Level 3 \| Fair Value, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-marketable equity securities	23,900,000		23,900,000			11,800,000
Biomatrica, Inc
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Contingent consideration, liability	20,000,000.0		20,000,000.0
Epic Sciences
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment owned, at fair value	$ 10,800,000		$ 10,800,000			10,800,000
Investment owned (in shares)	18,258,838		18,258,838
Thrive
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment owned, at fair value	$ 12,500,000		$ 12,500,000			1,000,000.0
Investment owned (in shares)	5,025,764		5,025,764
Thrive \| Series B Preferred Stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment owned (in shares)					4,000,000.0
Non-marketable equity investment					$ 10,000,000.0
Investment income, net	$ 1,500,000
Thrive \| Series A Preferred Stock
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-marketable equity investment						$ 1,000,000.0