SUPPLEMENTAL CONSOLIDATED BALANCE SHEETS AND STATEMENTS OF OPERATIONS INFORMATION - Schedule of Other Income (Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Supplemental Consolidated Balance Sheet & Statement of Operations Information [Abstract]
Document Fiscal Year Focus			2018
Interest income	$ 1,836	$ 659	$ 3,345	$ 1,261
Interest expense	(5,228)	(4,948)	(10,721)	(10,267)
Gains (losses), net on changes in fair value of investments	(3,035)	(1,448)	(8,068)	(1,145)
Foreign currency gains (losses), net	(12,533)	10,826	(11,135)	10,877
Impairments of investments	(9,189)		(10,044)	0
Other	1,692	789	1,651	550
Other income (expense), net	$ (26,457)	$ 5,878	$ (34,972)	$ 1,276