Summary of Significant Accounting Policies - Narrative (Details) - USD ($) |
3 Months Ended | |
|---|---|---|
Mar. 31, 2019 |
Mar. 31, 2018 |
|
| Accounting Policies [Abstract] | ||
| Realized gains (losses) recognized on available-for-sale investments | $ 0 | $ (200,000) |
| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). Reference 1: http://www.xbrl.org/2003/role/recommendedDisclosureRef
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