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FAIR VALUE MEASUREMENTS - SECURITIES WITH UNREALIZED LOSSES (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
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Schedule Of Available For Sale Securities [Line Items] |  |
Less Than 12 Months - Estimated Fair Value | $ 56,850 | $ 46,277
Less Than 12 Months - Gross Unrealized Losses | (33) | (25)
Total - Estimated Fair Value | 56,850 | 46,277
Total - Gross Unrealized Losses | (33) | (25)
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 |
Less Than 12 Months - Gross Unrealized Losses | (1) |
Total - Estimated Fair Value | 4,999 |
Total - Gross Unrealized Losses | (1) |
Commercial paper (due in less than one year) |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Less Than 12 Months - Estimated Fair Value | 22,956 | 8,571
Less Than 12 Months - Gross Unrealized Losses | (8) | (3)
Total - Estimated Fair Value | 22,956 | 8,571
Total - Gross Unrealized Losses | (8) | (3)
Corporate notes (due in less than one year) |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Less Than 12 Months - Estimated Fair Value | 12,573 | 26,082
Less Than 12 Months - Gross Unrealized Losses | (7) | (13)
Total - Estimated Fair Value | 12,573 | 26,082
Total - Gross Unrealized Losses | (7) | (13)
Corporate notes (due in one to two years) |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Less Than 12 Months - Estimated Fair Value | 16,322 | 11,624
Less Than 12 Months - Gross Unrealized Losses | (17) | (9)
Total - Estimated Fair Value | 16,322 | 11,624
Total - Gross Unrealized Losses | $ (17) | $ (9)

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