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FINANCIAL INSTRUMENTS | 9 Months Ended
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Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract] |
Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] | FINANCIAL INSTRUMENTS Cash, Cash Equivalents and Marketable Securities:
(In thousands) | Adjusted Cost |  | Unrealized Gains |  | Fair Value(3) |  | Cash and Cash Equivalents (1) |  | Short-term Marketable Securities
Cash | $ | 5,774 |  |  | $ | — |  |  | $ | 5,774 |  |  | $ | 5,774 |  |  | $ | — |
Level 1 (2) |  |  |  |  |  |  |  |  |
U.S. Treasury Securities, maturities less than three months | $ | 34,889 |  |  | $ | — |  |  | $ | 34,889 |  |  | $ | 34,889 |  |  | $ | — |
U.S. Treasury Securities, maturities greater than three months | $ | 55,433 |  |  | $ | 47 |  |  | $ | 55,480 |  |  | $ | — |  |  | $ | 55,480 |
Total | $ | 96,096 |  |  | $ | 47 |  |  | $ | 96,143 |  |  | $ | 40,663 |  |  | $ | 55,480 |
(1) The company considers all highly liquid instruments with maturities of three months or less at the time of purchase to be cash equivalents. (2) The fair value of the debt securities consisting of U.S. Treasury bills is based on their quoted market prices. The fair value of these financial instruments are classified as Level 1 in the fair value hierarchy. (3) ASC 825-10, Financial Instruments, allows entities to voluntarily choose to measure certain financial assets and liabilities at fair value (fair value option). The fair value option may be elected on an instrument-by-instrument basis and is irrevocable, unless a new election date occurs. If the fair value option is elected for an instrument, unrealized gains and losses for that instrument should be reported in earnings at each subsequent reporting date. At the date of purchase, the Company elected the fair value option for all investments with maturities of three months or greater at the time of purchase.

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- Definition The entire disclosure for investments in certain debt and equity securities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 320 -URI http://asc.fasb.org/subtopic&trid=2209399 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -URI http://asc.fasb.org/subtopic&trid=2324412 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -URI http://asc.fasb.org/topic&trid=2196928 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 940 -SubTopic 320 -URI http://asc.fasb.org/subtopic&trid=2176304 + Details
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