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FAIR VALUE MEASUREMENTS - SECURITIES WITH UNREALIZED LOSSES (Details) - USD ($) $ in Thousands | Dec. 31, 2015 | Dec. 31, 2014
--- | --- | ---
Marketable securities with unrealized losses |  |
Less Than 12 Months - Estimated Fair Value | $ 101,501 | $ 111,321
Less Than 12 Months - Gross Unrealized Losses | (256) | (100)
More Than 12 Months - Estimated Fair Value | 6,301 |
More Than 12 Months - Gross Unrealized Losses | (7) |
Total - Estimated Fair Value | 107,802 | 111,321
Total - Gross Unrealized Losses | (263) | (100)
Government-sponsored enterprise securities (due in less than 1 year) |  |
Marketable securities with unrealized losses |  |
Less Than 12 Months - Estimated Fair Value |  | 400
Less Than 12 Months - Gross Unrealized Losses |  | (1)
Total - Estimated Fair Value |  | 400
Total - Gross Unrealized Losses |  | (1)
Government-sponsored enterprise securities (due in 1 to 2 years) |  |
Marketable securities with unrealized losses |  |
Less Than 12 Months - Estimated Fair Value | 9,950 | 5,549
Less Than 12 Months - Gross Unrealized Losses | (57) | (7)
Total - Estimated Fair Value | 9,950 | 5,549
Total - Gross Unrealized Losses | (57) | (7)
Commercial paper (due in less than 1 year) |  |
Marketable securities with unrealized losses |  |
Less Than 12 Months - Estimated Fair Value | 7,834 |
Less Than 12 Months - Gross Unrealized Losses | (2) |
Total - Estimated Fair Value | 7,834 |
Total - Gross Unrealized Losses | (2) |
Corporate notes (due in less than 1 year) |  |
Marketable securities with unrealized losses |  |
Less Than 12 Months - Estimated Fair Value | 61,006 | 92,989
Less Than 12 Months - Gross Unrealized Losses | (71) | (63)
More Than 12 Months - Estimated Fair Value | 6,301 |
More Than 12 Months - Gross Unrealized Losses | (7) |
Total - Estimated Fair Value | 67,307 | 92,989
Total - Gross Unrealized Losses | (78) | (63)
Corporate notes (due in 1 to 2 years) |  |
Marketable securities with unrealized losses |  |
Less Than 12 Months - Estimated Fair Value | 22,711 | 12,383
Less Than 12 Months - Gross Unrealized Losses | (126) | (29)
Total - Estimated Fair Value | 22,711 | 12,383
Total - Gross Unrealized Losses | $ (126) | $ (29)

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