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MARKETABLE SECURITITES Marketable Securities (Details) - USD ($) $ in Thousands | Sep. 30, 2019 | Dec. 31, 2018
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 164,116 | $ 94,717
Gross Unrealized Gains | 538 | 2
Gross Unrealized Losses | (5) | (268)
Estimated Fair Market Value | 164,649 | 94,451
Investments due in 3 months or less: |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 4,141 | 6,788
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | (2)
Estimated Fair Market Value | 4,141 | 6,786
Investments due in 4-12 months: |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 68,989 | 60,123
Gross Unrealized Gains | 310 | 0
Gross Unrealized Losses | 0 | (244)
Estimated Fair Market Value | 69,299 | 59,879
Investments due in 12 months or greater: |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 90,986 | 27,806
Gross Unrealized Gains | 228 | 2
Gross Unrealized Losses | (5) | (22)
Estimated Fair Market Value | 91,209 | 27,786
Commercial paper | Investments due in 3 months or less: |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 3,241 |
Gross Unrealized Gains | 0 |
Gross Unrealized Losses | 0 |
Estimated Fair Market Value | 3,241 |
Corporate securities | Investments due in 3 months or less: |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 900 | 6,788
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | (2)
Estimated Fair Market Value | 900 | 6,786
Corporate securities | Investments due in 4-12 months: |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 68,989 | 60,123
Gross Unrealized Gains | 310 | 0
Gross Unrealized Losses | 0 | (244)
Estimated Fair Market Value | 69,299 | 59,879
Corporate securities | Investments due in 12 months or greater: |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 90,986 | 27,806
Gross Unrealized Gains | 228 | 2
Gross Unrealized Losses | (5) | (22)
Estimated Fair Market Value | $ 91,209 | $ 27,786

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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) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
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