FAIR VALUE MEASUREMENTS - Fair Value, Assets and Liabilities, Reconciliation of Level 3 Inputs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Apr. 30, 2018	Mar. 21, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investments	$ 1,405	$ 73,902	$ 82,966		$ 400	$ 82,584
Available-for-sale Securities	0	10,340
(Gain) loss from changes in fair value of investments	(72,497)	(9,064)	382
Reclassification of contingent liability to non-fair value	0	0	6,778
Business Combination, Contingent Consideration, Liability				$ 2,500
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value	1,298	1,529	0			14,588
Redeemable Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value option investments	0	10,340	15,431			$ 17,444
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	(379)	379	931
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities	9,961	5,470	2,944
Convertible Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0	1,148	$ 437
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investments	1,405	73,902
Fair Value, Recurring [Member] | Redeemable Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0	10,340
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investments	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Redeemable Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investments	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Redeemable Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investments	1,405	73,902
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value	1,298	1,529
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Redeemable Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	$ 0	$ 10,340