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MARKETABLE SECURITITES Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 92,833	$ 94,717
Gross Unrealized Gains	137	2
Gross Unrealized Losses	(69)	(268)
Estimated Fair Market Value	92,901	94,451
Investments due in 3 months or less:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	12,635	6,788
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(9)	(2)
Estimated Fair Market Value	12,626	6,786
Investments due in 4-12 months:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	60,573	60,123
Gross Unrealized Gains	53	0
Gross Unrealized Losses	(60)	(244)
Estimated Fair Market Value	60,566	59,879
Investments due in 12 months or greater:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	19,625	27,806
Gross Unrealized Gains	84	2
Gross Unrealized Losses	0	(22)
Estimated Fair Market Value	19,709	27,786
Corporate securities | Investments due in 3 months or less:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	12,635	6,788
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(9)	(2)
Estimated Fair Market Value	12,626	6,786
Corporate securities | Investments due in 4-12 months:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	60,573	60,123
Gross Unrealized Gains	53	0
Gross Unrealized Losses	(60)	(244)
Estimated Fair Market Value	60,566	59,879
Corporate securities | Investments due in 12 months or greater:
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	19,625	27,806
Gross Unrealized Gains	84	2
Gross Unrealized Losses	0	(22)
Estimated Fair Market Value	$ 19,709	$ 27,786

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

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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=82897076&loc=d3e27161-111563

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