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Investments (Tables) | 3 Months Ended
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Mar. 31, 2019
Investments, Debt and Equity Securities [Abstract] |
Short-Term and Long-Term Investments Available-for-Sale and Cost Method Investments | The fair value of investments classified as short-term consists of the following:
|  | March 31, 2019 |  |  | December 31, 2018 |
Available-for-sale investments: |  |  |  |  |  |  |  |
Time deposits and certificates of deposit |  | $ | 101 |  |  | $ | 102 |
Bankers’ acceptance drafts |  |  | 1,722 |  |  |  | 989 |
Asset-backed securities |  |  | — |  |  |  | 9,113 |
Commercial paper |  |  | 33,509 |  |  |  | 19,359 |
Corporate obligations |  |  | 8,994 |  |  |  | 9,352 |
U.S. treasury obligations |  |  | — |  |  |  | 13,298 |
U.S. agency obligations |  |  | — |  |  |  | 21,613 |
|  | $ | 44,326 |  |  | $ | 73,826 |
Investments classified as long-term consist of the following:
|  | March 31, 2019 |  |  | December 31, 2018 |
Available-for-sale investments: |  |  |  |  |  |  |  |
Group insurance contracts |  | $ | 5,950 |  |  | $ | 5,890 |
Cost method investments: |  |  |  |  |  |  |  |
Minority interest in a private company |  |  | 4,400 |  |  |  | 4,400 |
|  | $ | 10,350 |  |  | $ | 10,290 |
Gross Unrealized Gains and (Losses) Aggregated by Investment Category | The following tables show the gross unrealized gains and (losses) aggregated by investment category for available-for-sale investments:
As of March 31, 2019: |  | Cost |  |  | Gross Unrealized Gains |  |  | Gross Unrealized (Losses) |  |  | Estimated Fair Value |
Short-term investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Available-for-sale investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Time deposits and certificates of deposit |  | $ | 99 |  |  | $ | 2 |  |  | $ | — |  |  | $ | 101 |
Bankers’ acceptance drafts |  |  | 1,722 |  |  |  | — |  |  |  | — |  |  |  | 1,722 |
Commercial paper |  |  | 33,752 |  |  |  | 1 |  |  |  | (244 | ) |  |  | 33,509 |
Corporate obligations |  |  | 8,996 |  |  |  | 1 |  |  |  | (3 | ) |  |  | 8,994 |
|  | $ | 44,569 |  |  | $ | 4 |  |  | $ | (247 | ) |  | $ | 44,326 |
As of March 31, 2019: |  | Cost |  |  | Gross Unrealized Gains |  |  | Gross Unrealized (Losses) |  |  | Estimated Fair Value |
Long-term investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Available-for-sale investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Group insurance contracts |  | $ | 5,582 |  |  | $ | 368 |  |  | $ | — |  |  | $ | 5,950 |
As of December 31, 2018: |  | Cost |  |  | Gross Unrealized Gains |  |  | Gross Unrealized (Losses) |  |  | Estimated Fair Value |
Short-term investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Available-for-sale investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Time deposits and certificates of deposit |  | $ | 102 |  |  | $ | — |  |  | $ | — |  |  | $ | 102 |
Bankers’ acceptance drafts |  |  | 989 |  |  |  | — |  |  |  | — |  |  |  | 989 |
Asset-backed securities |  |  | 9,121 |  |  |  | 1 |  |  |  | (9 | ) |  |  | 9,113 |
Commercial paper |  |  | 19,504 |  |  |  | — |  |  |  | (145 | ) |  |  | 19,359 |
Corporate obligations |  |  | 9,367 |  |  |  | — |  |  |  | (15 | ) |  |  | 9,352 |
U.S. treasury obligations |  |  | 13,294 |  |  |  | 4 |  |  |  | — |  |  |  | 13,298 |
U.S. agency obligations |  |  | 21,617 |  |  |  | 2 |  |  |  | (6 | ) |  |  | 21,613 |
|  | $ | 73,994 |  |  | $ | 7 |  |  | $ | (175 | ) |  | $ | 73,826 |
As of December 31, 2018: |  | Cost |  |  | Gross Unrealized Gains |  |  | Gross Unrealized (Losses) |  |  | Estimated Fair Value |
Long-term investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Available-for-sale investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Group insurance contracts |  | $ | 5,546 |  |  | $ | 344 |  |  | $ | — |  |  | $ | 5,890 |

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- Definition Tabular disclosure of the reconciliation of available-for-sale securities from cost basis to fair value. + References No definition available. + Details
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