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FAIR VALUE MEASUREMENTS - SECURITIES WITH UNREALIZED LOSSES (Details) - USD ($) $ in Thousands | Sep. 30, 2019 | Dec. 31, 2018
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Schedule Of Available For Sale Securities [Line Items] |  |
Less Than 12 Months - Estimated Fair Value | $ 20,749 | $ 107,767
Less Than 12 Months - Gross Unrealized Losses | (23) | (176)
12 Months or Longer - Estimated Fair Value |  | 14,221
12 Months or Longer - Gross Unrealized Losses |  | (36)
Total - Estimated Fair Value | 20,749 | 121,988
Total - Gross Unrealized Losses | (23) | (212)
Government-sponsored enterprise securities (due in one to two years) |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Less Than 12 Months - Estimated Fair Value | 8,484 |
Less Than 12 Months - Gross Unrealized Losses | (15) |
Total - Estimated Fair Value | 8,484 |
Total - Gross Unrealized Losses | (15) |
Commercial paper (due in less than one year) |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Less Than 12 Months - Estimated Fair Value |  | 22,628
Less Than 12 Months - Gross Unrealized Losses |  | (29)
Total - Estimated Fair Value |  | 22,628
Total - Gross Unrealized Losses |  | (29)
Corporate notes (due in less than one year) |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Less Than 12 Months - Estimated Fair Value | 9,256 | 66,557
Less Than 12 Months - Gross Unrealized Losses | (5) | (82)
12 Months or Longer - Estimated Fair Value |  | 14,221
12 Months or Longer - Gross Unrealized Losses |  | (36)
Total - Estimated Fair Value | 9,256 | 80,778
Total - Gross Unrealized Losses | (5) | (118)
Corporate notes (due in one to two years) |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Less Than 12 Months - Estimated Fair Value | 3,009 | 18,582
Less Than 12 Months - Gross Unrealized Losses | (3) | (65)
Total - Estimated Fair Value | 3,009 | 18,582
Total - Gross Unrealized Losses | $ (3) | $ (65)

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- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=118942371&loc=SL82922954-210456 + Details
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- Definition Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455 + Details
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