SUPPLEMENTAL CONSOLIDATED BALANCE SHEETS AND STATEMENTS OF OPERATIONS INFORMATION - Schedule of Other Income (Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplemental Consolidated Balance Sheet & Statement of Operations Information [Abstract]
Interest income	$ 7,744	$ 6,420	$ 3,287
Interest expense	(23,593)	(21,909)	(20,680)
Gains (losses), net on changes in fair value of investments	(72,497)	(9,064)	382
Gain on sale of investment	(412)	0	7,624
Foreign currency gains (losses), net	(5,960)	(20,325)	18,634
Impairments of investments	(9,961)	(10,156)	(2,944)
Equity Securities without Readily Determinable Fair Value, Upward Price Adjustment, Annual Amount	51,397
Observable Price Change Adjustments, Investments, Upward Adjustment	51,397	0	0
Other	(47)	2,026	407
Other income (expense), net	$ (53,329)	$ (53,008)	$ 6,710