FAIR VALUE MEASUREMENTS - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Mar. 21, 2017	Dec. 31, 2016	Apr. 04, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities without Readily Determinable Fair Value, Upward Price Adjustment, Annual Amount	$ 51,397
Class of Warrant or Right, Exercise Price of Warrants or Rights						$ 8.50
Equity method investments	1,405	$ 73,902	$ 82,966	$ 400	$ 82,584
(Gain) loss from changes in fair value of investments	(72,497)	(9,064)	382
Payment for Contingent Consideration Liability, Operating Activities	(312)	0	7,858
Reclassification of contingent liability to non-fair value	0	0	6,778
(Gain) loss, net from changes in fair value of contingent consideration	39	56	48
Foreign Currency Contracts, Liability, Fair Value Disclosure	(42)	116	0
Contingent consideration liability incurred in connection with acquisition of business	0	1,589	0
Unrealized (Losses) Gains Still Held - Liabilities	39	56	0
Restructuring charges	31	(136)	18,828
Investments, Fair Value Disclosure	1,405	84,242
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(72,497)	(9,064)	382
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value	1,298	1,529	0		14,588
Convertible Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payments to Acquire Investments	0	0	1,612
Redeemable Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	0	10,340	15,431		17,444
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities	(9,961)	(5,470)	(2,944)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	379	(379)	(931)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(10,340)	(5,091)	(2,013)
Convertible Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Proceeds from Convertible Debt	0	(8,594)	(1,843)
available-for-sale investment transfer to other equity investment	0	(4,008)	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0	(1,148)	(437)
Unrealized Gain (Loss) on Securities	0	2,396	1,984
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0	1,303
Debt Securities, Available-for-sale	$ 0	0	$ 11,354		$ 10,038
Other Equity Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities		$ (4,600)