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Significant Accounting Policies - Summary of Derivative Financial Instruments (Details) - Fair Value, Measurements, Recurring - Black Scholes Model - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Liabilities:
Fair value, liabilities		$ 9,578
Warrants
Liabilities:
Fair value, liabilities	$ 13,769	6,941
Non-employee Stock Options
Liabilities:
Fair value, liabilities		2,637
Non-current Receivable
Assets:
Fair value, assets	294
Level 3
Liabilities:
Fair value, liabilities		9,578
Level 3 | Warrants
Liabilities:
Fair value, liabilities	13,769	6,941
Level 3 | Non-employee Stock Options
Liabilities:
Fair value, liabilities		$ 2,637
Level 3 | Non-current Receivable
Assets:
Fair value, assets	$ 294

X

- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ 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)
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Fair value of financial and nonfinancial obligations.

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-SubTopic 10
-Section 50
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