CASH, CASH EQUIVALENTS AND INVESTMENTS - Schedule of Cash, Cash Equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Cash And Cash Equivalents [Line Items]
Cash Equivalents, at Carrying Value	$ 222,738	$ 131,627
Cash Equivalents, Gross Unrealized Gains	7
Cash Equivalents, Gross Unrealized Losses	(1)
Cash and Cash Equivalents, Fair Value Disclosure	222,744	131,627
Cash Accounts in Banking Institutions [Member]
Cash And Cash Equivalents [Line Items]
Cash Equivalents, at Carrying Value	108,664	119,272
Cash and Cash Equivalents, Fair Value Disclosure	108,664	119,272
Money Market Accounts [Member]
Cash And Cash Equivalents [Line Items]
Cash Equivalents, at Carrying Value	14,085	12,355
Cash and Cash Equivalents, Fair Value Disclosure	14,085	$ 12,355
U.S. Government Bonds [Member]
Cash And Cash Equivalents [Line Items]
Cash Equivalents, at Carrying Value	99,989
Cash Equivalents, Gross Unrealized Gains	7
Cash Equivalents, Gross Unrealized Losses	(1)
Cash and Cash Equivalents, Fair Value Disclosure	$ 99,995