Cash Equivalents and Marketable Securities - Additional Information (Details) - USD ($) |
3 Months Ended | 12 Months Ended |
|---|---|---|
Mar. 31, 2019 |
Dec. 31, 2018 |
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| Cash And Cash Equivalents [Line Items] | ||
| Long-term marketable securities | $ 13,747,000 | |
| Marketable Securities | ||
| Cash And Cash Equivalents [Line Items] | ||
| Recognition of other-than-temporary impairment | $ 0 | |
| Maximum [Member] | ||
| Cash And Cash Equivalents [Line Items] | ||
| Marketable securities maturity period | 1 year | 1 year |
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- Definition Marketable securities maturity period. No definition available.
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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- Definition Amount of investment in marketable security, classified as noncurrent. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount of other-than-temporary impairment (OTTI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), recognized in earnings. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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