INTEREST AND OTHER, NET (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Other Income and Expenses [Abstract]
Interest expense	$ (77)		$ (871)	$ (91)	$ (2,042)
Interest income and gains on short-term investments, net	3,792		972	6,795	1,939
Foreign exchange loss, net	(1,800)		(399)	(4,052)	(579)
Gain on investments in privately-held companies	441		0	9,569	0
Impairment of investment in a privately-held company	0	$ (1,800)	0	(1,755)	0
Other	(88)		(40)	33	(189)
Interest and other, net	$ 2,268		$ (338)	$ 10,499	$ (871)