SUPPLEMENTAL CONSOLIDATED BALANCE SHEETS AND STATEMENTS OF OPERATIONS INFORMATION - Schedule of Other Income (Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Consolidated Balance Sheet & Statement of Operations Information [Abstract]
Interest income	$ 6,420	$ 3,287	$ 1,808
Interest expense	(21,909)	(20,680)	(15,912)
Gains (losses), net on changes in fair value of investments	(9,064)	382	(48,141)
Gain on sale of investment	0	7,624	0
Foreign currency gains (losses), net	(20,325)	18,634	(6,927)
Impairments of investments	(10,156)	(2,944)	0
Other	2,026	407	(2,117)
Other income (expense), net	$ (53,008)	$ 6,710	$ (71,289)