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FAIR VALUE MEASUREMENTS - SECURITIES WITH UNREALIZED LOSSES (Details) - USD ($) $ in Thousands | Mar. 31, 2021 | Dec. 31, 2020
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Schedule Of Available For Sale Securities [Line Items] |  |
Less Than 12 Months - Estimated Fair Value | $ 69,097 | $ 56,850
Less Than 12 Months - Gross Unrealized Losses | (34) | (33)
Total - Estimated Fair Value | 69,097 | 56,850
Total - Gross Unrealized Losses | (34) | (33)
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 | 4,999 | 4,999
Less Than 12 Months - Gross Unrealized Losses | (1) | (1)
Total - Estimated Fair Value | 4,999 | 4,999
Total - Gross Unrealized Losses | (1) | (1)
Commercial paper (due in less than one year) |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Less Than 12 Months - Estimated Fair Value | 21,987 | 22,956
Less Than 12 Months - Gross Unrealized Losses | (2) | (8)
Total - Estimated Fair Value | 21,987 | 22,956
Total - Gross Unrealized Losses | (2) | (8)
Corporate notes (due in less than one year) |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Less Than 12 Months - Estimated Fair Value | 29,540 | 12,573
Less Than 12 Months - Gross Unrealized Losses | (11) | (7)
Total - Estimated Fair Value | 29,540 | 12,573
Total - Gross Unrealized Losses | (11) | (7)
Corporate notes (due in one to two years) |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Less Than 12 Months - Estimated Fair Value | 12,571 | 16,322
Less Than 12 Months - Gross Unrealized Losses | (20) | (17)
Total - Estimated Fair Value | 12,571 | 16,322
Total - Gross Unrealized Losses | $ (20) | $ (17)

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