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FAIR VALUE MEASUREMENTS - SECURITY TYPE (Details) - USD ($) $ in Thousands | Sep. 30, 2016 | Dec. 31, 2015
--- | --- | ---
Included in cash and cash equivalents |  |
Amortized Cost | $ 5,369 | $ 19,177
Gross Unrealized Losses |  | (1)
Estimated Fair Value | 5,369 | 19,176
Restricted cash |  |
Amortized Cost | 268 | 267
Estimated Fair Value | 268 | 267
Marketable securities |  |
Amortized Cost | 123,635 | 125,397
Gross Unrealized Gains | 78 | 50
Gross Unrealized Losses | (53) | (262)
Estimated Fair Value | 123,660 | 125,185
Money market funds |  |
Included in cash and cash equivalents |  |
Amortized Cost | 5,369 | 4,577
Estimated Fair Value | 5,369 | 4,577
Commercial paper |  |
Included in cash and cash equivalents |  |
Amortized Cost |  | 7,599
Estimated Fair Value |  | 7,599
Government-sponsored enterprise securities |  |
Included in cash and cash equivalents |  |
Amortized Cost |  | 1,999
Estimated Fair Value |  | 1,999
Corporate notes |  |
Included in cash and cash equivalents |  |
Amortized Cost |  | 5,002
Gross Unrealized Losses |  | (1)
Estimated Fair Value |  | 5,001
Certificate of deposit |  |
Restricted cash |  |
Amortized Cost | 268 | 267
Estimated Fair Value | 268 | 267
Government-sponsored enterprise securities (due in one to two years) |  |
Marketable securities |  |
Amortized Cost | 17,502 | 10,007
Gross Unrealized Gains | 2 |
Gross Unrealized Losses | (7) | (57)
Estimated Fair Value | 17,497 | 9,950
Commercial paper (due in less than one year) |  |
Marketable securities |  |
Amortized Cost | 39,253 | 27,661
Gross Unrealized Gains | 66 | 49
Gross Unrealized Losses | (9) | (2)
Estimated Fair Value | 39,310 | 27,708
Corporate notes (due in less than one year) |  |
Marketable securities |  |
Amortized Cost | 63,371 | 64,892
Gross Unrealized Gains | 7 | 1
Gross Unrealized Losses | (33) | (77)
Estimated Fair Value | 63,345 | 64,816
Corporate notes (due in one to two years) |  |
Marketable securities |  |
Amortized Cost | 3,509 | 22,837
Gross Unrealized Gains | 3 |
Gross Unrealized Losses | (4) | (126)
Estimated Fair Value | $ 3,508 | $ 22,711

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