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Fair Value of Financial Assets and Liabilities - Schedule of Assets and Liabilities Measured at Fair Value (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands | Mar. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Assets: |  |
Cash equivalents | $ 22,299 | $ 8,134
Liabilities: |  |
Derivative liability | 18 | 5,148
Total | 18 | 5,148
Preferred Stock Warrant Liability [Member] |  |
Liabilities: |  |
Derivative liability |  | 4,947
Total |  | 4,947
Derivative Liability [Member] |  |
Liabilities: |  |
Derivative liability | 18 | 201
Total | 18 | 201
Money Market Funds [Member] |  |
Assets: |  |
Cash equivalents | 22,299 | 8,134
Level 2 [Member] |  |
Assets: |  |
Cash equivalents | 22,299 | 8,134
Level 2 [Member] | Money Market Funds [Member] |  |
Assets: |  |
Cash equivalents | 22,299 | 8,134
Level 3 [Member] |  |
Liabilities: |  |
Derivative liability | 18 | 5,148
Total | 18 | 5,148
Level 3 [Member] | Preferred Stock Warrant Liability [Member] |  |
Liabilities: |  |
Derivative liability |  | 4,947
Total |  | 4,947
Level 3 [Member] | Derivative Liability [Member] |  |
Liabilities: |  |
Derivative liability | 18 | 201
Total | $ 18 | $ 201

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- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References No definition available. + Details
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- Definition Fair value of financial and nonfinancial obligations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258 + Details
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