Cash, Cash Equivalents and Investments - Narrative (Details) - USD ($) |
12 Months Ended | |
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Dec. 31, 2018 |
Dec. 31, 2017 |
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| Cash and Cash Equivalents [Abstract] | ||
| Realized gain (loss) on investments | $ 1,000,000 | $ 0 |
| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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