Non-Marketable Investments - Additional Information (Details) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
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| Equity Method Investments And Joint Ventures [Abstract] | |||
| Carrying value of investment in privately-held companies | $ 43,600,000 | $ 22,700,000 | |
| Equity method investment, realized gain (loss) | (2,200,000) | 1,000,000 | $ (3,900,000) |
| Impairment on investment | $ 7,200,000 | $ 0 | $ 0 |
| X | ||||||||||
- Definition Amount of gain (loss) on sale or disposal of an equity method investment. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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