FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS - Narrative (Details)	3 Months Ended
	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contractual maturity of current available-for-sale securities (less than)	1 year
Available-for-sale marketable debt securities in a continuous unrealized loss position for longer than twelve months	$ 0
Assets measured at fair value on a nonrecurring basis
Equity securities without readily determinable fair values	301,600,000		$ 353,100,000
Total upward adjustments to equity securities without readily determinable fair value	19,900,000
Total downward adjustments to equity securities without readily determinable fair value	58,100,000
Contingent Consideration Arrangements
Total maximum contingent payment	30,000,000.0
Gross fair value, before unamortized discount	1,300,000
Non-current portion of contingent consideration	600,000		$ 6,900,000
Impairment of equity securities without readily determinable fair value	51,500,000
Contingent Consideration Arrangements
Contingent Consideration Arrangements
Assumption of contingent consideration arrangement liability	1,000,000	$ 0
Settlements of contingent consideration arrangements	$ 1,000,000	$ 1,988,000
Discount Rate | Contingent Consideration Arrangements
Contingent Consideration Arrangements
Discount rate on contingent consideration (as a percent)	0.25		0.25