Organization and Summary of Significant Accounting Policies - Assumptions Used to Estimate the Fair Value of Stock Option Grants (Q3) (Details) - $ / shares	9 Months Ended	12 Months Ended
Sep. 30, 2018	Dec. 31, 2016
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Risk-free interest rate, minimum	2.27%	1.36%
Risk-free interest rate, maximum	2.29%	1.78%
Dividend yield	0.00%	0.00%
Forfeiture rate	0.00%	11.33%
Weighted average grant date fair value (in usd per share)	$ 1.66	$ 7.23
Minimum
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Volatility	98.09%
Expected term	5 years	5 years 3 months
Maximum
Share Based Payment Award Stock Options Valuation Assumptions [Line Items]
Volatility	105.01%
Expected term	6 years 29 days	6 years 29 days

Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Forfeiture Rate

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- Definition

Share Based Payment Award Stock Options Valuation Assumptions [Line Items]

+ References

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- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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- Definition

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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- Definition

The maximum risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

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- Definition

The minimum risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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- Definition

Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

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