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Investments (Tables) | 6 Months Ended
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Jun. 30, 2018
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:
|  | June 30, 2018 |  |  | December 31, 2017 |
Available-for-sale investments: |  |  |  |  |  |  |  |
Time deposits and certificates of deposit |  | $ | 18,455 |  |  | $ | 9,757 |
Bankers’ acceptance drafts |  |  | 2,522 |  |  |  | 5,330 |
Asset-backed securities |  |  | 34,727 |  |  |  | 36,990 |
Commercial paper |  |  | 25,925 |  |  |  | 13,750 |
Corporate obligations |  |  | 66,663 |  |  |  | 77,821 |
Municipal bonds |  |  | 2,615 |  |  |  | 1,970 |
U.S. treasury obligations |  |  | 31,434 |  |  |  | 28,078 |
U.S. agency obligations |  |  | 21,345 |  |  |  | 35,738 |
|  | $ | 203,686 |  |  | $ | 209,434 |
Investments classified as long-term consist of the following:
|  | June 30, 2018 |  |  | December 31, 2017 |
Available-for-sale investments: |  |  |  |  |  |  |  |
Group insurance contracts |  | $ | 6,076 |  |  | $ | 6,255 |
Cost method investments: |  |  |  |  |  |  |  |
Minority interest in a private company |  |  | 4,400 |  |  |  | 4,400 |
|  | $ | 10,476 |  |  | $ | 10,655 |
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 June 30, 2018: |  | Cost |  |  | Gross Unrealized Gains |  |  | Gross Unrealized (Losses) |  |  | Estimated Fair Value |
Short-term investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Available-for-sale investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Time deposits and certificates of deposit |  | $ | 18,452 |  |  | $ | 3 |  |  | $ | — |  |  | $ | 18,455 |
Bankers’ acceptance drafts |  |  | 2,522 |  |  |  | — |  |  |  | — |  |  |  | 2,522 |
Asset-backed securities |  |  | 34,760 |  |  |  | 9 |  |  |  | (42 | ) |  |  | 34,727 |
Commercial paper |  |  | 26,337 |  |  |  | — |  |  |  | (412 | ) |  |  | 25,925 |
Corporate obligations |  |  | 66,632 |  |  |  | 59 |  |  |  | (28 | ) |  |  | 66,663 |
Municipal bonds |  |  | 2,620 |  |  |  | — |  |  |  | (5 | ) |  |  | 2,615 |
U.S. treasury obligations |  |  | 31,418 |  |  |  | 16 |  |  |  | — |  |  |  | 31,434 |
U.S. agency obligations |  |  | 21,341 |  |  |  | 5 |  |  |  | (1 | ) |  |  | 21,345 |
|  | $ | 204,082 |  |  | $ | 92 |  |  | $ | (488 | ) |  | $ | 203,686 |
As of June 30, 2018: |  | Cost |  |  | Gross Unrealized Gains |  |  | Gross Unrealized (Losses) |  |  | Estimated Fair Value |
Long-term investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Available-for-sale investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Group insurance contracts |  | $ | 6,051 |  |  | $ | 25 |  |  | $ | — |  |  | $ | 6,076 |
As of December 31, 2017: |  | Cost |  |  | Gross Unrealized Gains |  |  | Gross Unrealized (Losses) |  |  | Estimated Fair Value |
Short-term investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Available-for-sale investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Time deposits and certificates of deposit |  | $ | 9,756 |  |  | $ | 1 |  |  | $ | — |  |  | $ | 9,757 |
Bankers acceptance drafts |  |  | 5,330 |  |  |  | — |  |  |  | — |  |  |  | 5,330 |
Asset-backed securities |  |  | 37,017 |  |  |  | 15 |  |  |  | (42 | ) |  |  | 36,990 |
Commercial paper |  |  | 13,810 |  |  |  | — |  |  |  | (60 | ) |  |  | 13,750 |
Corporate obligations |  |  | 77,788 |  |  |  | 58 |  |  |  | (25 | ) |  |  | 77,821 |
Municipal bonds |  |  | 1,970 |  |  |  | — |  |  |  | — |  |  |  | 1,970 |
U.S. treasury obligations |  |  | 28,054 |  |  |  | 24 |  |  |  | — |  |  |  | 28,078 |
U.S. agency obligations |  |  | 35,728 |  |  |  | 10 |  |  |  | — |  |  |  | 35,738 |
|  | $ | 209,453 |  |  | $ | 108 |  |  | $ | (127 | ) |  | $ | 209,434 |
As of December 31, 2017: |  | Cost |  |  | Gross Unrealized Gains |  |  | Gross Unrealized (Losses) |  |  | Estimated Fair Value |
Long-term investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Available-for-sale investments: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Group insurance contracts |  | $ | 6,006 |  |  | $ | 249 |  |  | $ | — |  |  | $ | 6,255 |

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- Definition Investments classified as short-term and long-term available-for-sale investments and long-term cost method investments. + References No definition available. + Details
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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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