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FAIR VALUE MEASUREMENTS - SECURITIES WITH UNREALIZED LOSSES (Details) - USD ($) $ in Thousands | Sep. 30, 2021 | Dec. 31, 2020
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Schedule Of Available For Sale Securities [Line Items] |  |
Less Than 12 Months - Estimated Fair Value | $ 72,445 | $ 56,850
Less Than 12 Months - Gross Unrealized Losses | (38) | (33)
Total - Estimated Fair Value | 72,445 | 56,850
Total - Gross Unrealized Losses | (38) | (33)
Municipal securities (due in one to two years) |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Less Than 12 Months - Estimated Fair Value | 2,999 |
Less Than 12 Months - Gross Unrealized Losses | (1) |
Total - Estimated Fair Value | 2,999 |
Total - Gross Unrealized Losses | (1) |
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 | 4,997 | 4,999
Less Than 12 Months - Gross Unrealized Losses | (3) | (1)
Total - Estimated Fair Value | 4,997 | 4,999
Total - Gross Unrealized Losses | (3) | (1)
Commercial paper (due in less than one year) |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Less Than 12 Months - Estimated Fair Value | 31,965 | 22,956
Less Than 12 Months - Gross Unrealized Losses | (10) | (8)
Total - Estimated Fair Value | 31,965 | 22,956
Total - Gross Unrealized Losses | (10) | (8)
Corporate notes (due in less than one year) |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Less Than 12 Months - Estimated Fair Value | 17,252 | 12,573
Less Than 12 Months - Gross Unrealized Losses | (8) | (7)
Total - Estimated Fair Value | 17,252 | 12,573
Total - Gross Unrealized Losses | (8) | (7)
Corporate notes (due in one to two years) |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Less Than 12 Months - Estimated Fair Value | 15,232 | 16,322
Less Than 12 Months - Gross Unrealized Losses | (16) | (17)
Total - Estimated Fair Value | 15,232 | 16,322
Total - Gross Unrealized Losses | $ (16) | $ (17)

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