MARKETABLE SECURITITES Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Interest receivable	$ 1,712	$ 1,279
Amortized Cost	232,552	231,815
Gross Unrealized Gains	207	589
Gross Unrealized Losses	(576)	(6)
Estimated Fair Market Value	232,183	232,398
Investments due in 3 months or less:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	42,973	15,934
Gross Unrealized Gains	1	18
Gross Unrealized Losses	(21)	0
Estimated Fair Market Value	42,953	15,952
Investments due in 4-12 months:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	63,204	71,223
Gross Unrealized Gains	61	269
Gross Unrealized Losses	(159)	0
Estimated Fair Market Value	63,106	71,492
Investments due in 12 months or greater:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	126,375	144,658
Gross Unrealized Gains	145	302
Gross Unrealized Losses	(396)	(6)
Estimated Fair Market Value	126,124	144,954
Commercial paper \| Investments due in 3 months or less:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	14,869
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Estimated Fair Market Value	14,869
Corporate securities \| Investments due in 3 months or less:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	28,104	15,934
Gross Unrealized Gains	1	18
Gross Unrealized Losses	(21)	0
Estimated Fair Market Value	28,084	15,952
Corporate securities \| Investments due in 4-12 months:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	63,204	71,223
Gross Unrealized Gains	61	269
Gross Unrealized Losses	(159)	0
Estimated Fair Market Value	63,106	71,492
Corporate securities \| Investments due in 12 months or greater:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	126,375	144,658
Gross Unrealized Gains	145	302
Gross Unrealized Losses	(396)	0
Estimated Fair Market Value	$ 126,124	$ 144,954

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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- Definition

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)
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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.

+ References

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

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- Definition

Carrying amount as of the balance sheet date of current interest earned but not received. Also called accrued interest or accrued interest receivable. For classified balance sheets, represents the current amount receivable, that is amounts expected to be collected within one year or the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.8)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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- Definition

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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