Financial Instruments - Summary of Changes in Fair Value of Warrants for Preferred Shares (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Balance at beginning of year	$ 3,612	$ 872
Changes in fair value of warrants for preferred shares	168	2,740
Issuance of warrants for preferred shares	$ (3,780)
Balance at end of year		$ 3,612

Fair value measurement with unobservable inputs reconciliation recurring basis liability issuance of warrants for preferred stock.

No definition available.

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- References

No definition available.

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- Definition

Amount of increase (decrease) of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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