MARKETABLE SECURITIES Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Interest receivable	$ 1,500	$ 1,500
Amortized Cost	278,765	373,400
Gross Unrealized Gains	0	21
Gross Unrealized Losses	(5,346)	(1,186)
Estimated Fair Market Value	273,419	372,235
Investments due in 3 months or less:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	7,949	97,250
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(3)
Estimated Fair Market Value	7,948	97,247
Investments due in 4-12 months:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	45,329	25,054
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(484)	(42)
Estimated Fair Market Value	44,845	25,012
Investments due in 12 months or greater:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	225,487	251,096
Gross Unrealized Gains	0	21
Gross Unrealized Losses	(4,861)	(1,141)
Estimated Fair Market Value	220,626	249,976
Commercial paper | Investments due in 3 months or less:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,996	89,965
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Market Value	5,996	89,965
Corporate securities | Investments due in 3 months or less:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,953	7,285
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	(3)
Estimated Fair Market Value	1,952	7,282
Corporate securities | Investments due in 4-12 months:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	45,329	25,054
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(484)	(42)
Estimated Fair Market Value	44,845	25,012
Corporate securities | Investments due in 12 months or greater:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	225,487	251,096
Gross Unrealized Gains	0	21
Gross Unrealized Losses	(4,861)	(1,141)
Estimated Fair Market Value	$ 220,626	$ 249,976