Warrants - Aggregate Fair Values, Inputs and Assumptions (Details) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares
Warrant
Fair value assumptions
Calculated aggregate value \| $	$ 482	$ 1,073
Weighted average exercise price per share (usd per share)	$ 29.69	$ 30.11
Closing price per share of common stock (usd per share)	$ 2.36	$ 3.20
Volatility \| Warrant
Fair value assumptions
Warrant liability, measurement input	0.918	0.922
Weighted average remaining expected life \| Warrant
Fair value assumptions
Weighted average remaining expected life	2 years 9 months	3 years 4 months
Risk-free interest rate \| Warrant
Fair value assumptions
Warrant liability, measurement input	0.0280	0.0200
Dividend yield
Fair value assumptions
Warrant liability, measurement input	0
Dividend yield \| Warrant
Fair value assumptions
Warrant liability, measurement input	0	0

Closing price per share of common stock.

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- Definition

It represents aggregate fair value of warrants.

+ References

No definition available.

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- Definition

Exercise price of the warrants.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column A

+ Details

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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.

+ References

No definition available.

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- Definition

Value of input used to measure outstanding warrant and right embodying unconditional obligation requiring redemption by transferring asset at specified or determinable date or upon event certain to occur.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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- Definition

Period between issuance and expiration of outstanding warrant and right embodying unconditional obligation requiring redemption by transferring asset at specified or determinable date or upon event certain to occur, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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