Cash, Cash Equivalents and Investments - Narrative (Details) - USD ($) |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2018 |
Jun. 30, 2017 |
Jun. 30, 2018 |
Jun. 30, 2017 |
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| Cash and Cash Equivalents [Abstract] | ||||
| Realized gains (losses) recognized on available-for-sale investments | $ 100,000 | $ (100,000) | ||
| Realized gains (losses) recognized on available-for-sale investments | $ 0 | $ 0 | ||
| X | ||||||||||
- Definition Debt Securities, Available-For-Sale, Realized Gain (Loss) No definition available.
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| X | ||||||||||
- Definition This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
- References No definition available.
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