MARKETABLE SECURITIES (Details) Securities in Thousands, $ in Thousands	Dec. 31, 2019 USD ($) Securities	Dec. 31, 2018 USD ($) Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 231,815	$ 94,717
Gross Unrealized Gains	589	2
Gross Unrealized Losses	(6)	(268)
Estimated Fair Market Value	$ 232,398	$ 94,451
Weighted Average Interest Rate on Investments	2.17%	2.65%
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions \| Securities	0	0
Investments due in 3 months or less:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 15,934	$ 6,788
Gross Unrealized Gains	18	0
Gross Unrealized Losses	0	(2)
Estimated Fair Market Value	15,952	6,786
Investments due in 4-12 months:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	71,223	60,123
Gross Unrealized Gains	269	0
Gross Unrealized Losses	0	(244)
Estimated Fair Market Value	71,492	59,879
Investments due in 12 months or greater:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	144,658	27,806
Gross Unrealized Gains	302	2
Gross Unrealized Losses	(6)	(22)
Estimated Fair Market Value	144,954	27,786
Corporate securities \| Investments due in 3 months or less:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	15,934	6,788
Gross Unrealized Gains	18	0
Gross Unrealized Losses	0	(2)
Estimated Fair Market Value	15,952	6,786
Corporate securities \| Investments due in 4-12 months:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	71,223	60,123
Gross Unrealized Gains	269	0
Gross Unrealized Losses	0	(244)
Estimated Fair Market Value	71,492	59,879
Corporate securities \| Investments due in 12 months or greater:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	144,658	27,806
Gross Unrealized Gains	302	2
Gross Unrealized Losses	(6)	(22)
Estimated Fair Market Value	$ 144,954	$ 27,786

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount of investment in debt and equity securities categorized neither as trading securities nor held-to-maturity securities and intended be sold or mature one year or operating cycle, if longer.

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Number of investment positions in available-for-sale investments in a continuous unrealized loss position for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27290-111563

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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