Combined purchase price of shares and common warrants.

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Gross proceeds from issuance of common stock and warrants.

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The estimated net proceeds to the Company from the offering, after deducting underwriters' discounts and commissions and other offering costs and expenses.

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Number of common warrants for each share.

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- Definition

The percentage of fixed commission expense of gross proceeds of shares sold in the ATM agreement.

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- Definition

Share price of shares of common stock underlying warrants.

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Number of consecutive trading days.

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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.

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Exercise price per share or per unit of warrants or rights outstanding.

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Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.

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Face amount or stated value per share of common stock.

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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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Amount of contractual obligation, including but not limited to, long-term debt, capital lease obligations, operating lease obligations, purchase obligations, and other commitments.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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The cash inflow from the additional capital contribution to the entity.

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The cash inflow associated with the amount received from entity's raising of capital via private rather than public placement.

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Price of a single share of a number of saleable stocks of a company.

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Per share or per unit amount of equity securities issued.

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Number of new stock issued during the period.

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Stockholders' Equity - Common Stock (Details) - USD ($) $ / shares in Units, $ in Millions				1 Months Ended		3 Months Ended	6 Months Ended
	Apr. 07, 2020	Dec. 23, 2019	Mar. 04, 2019	Jun. 30, 2020	Nov. 30, 2018	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	May 12, 2020	Dec. 31, 2019
Class of Stock
Par value (per share)				$ 0.001		$ 0.001	$ 0.001		$ 0.001	$ 0.001
Shares authorized (in shares)				140,000,000		140,000,000	140,000,000		140,000,000	140,000,000
Proceeds from issuance		$ 3.9
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any				$ 5.1
"At-The-Market" Equity Program
Class of Stock
Value of shares investor has committed to purchase from time to time at Company's sole discretion				46.8		$ 46.8	$ 46.8
Stock issued (in shares)							821,018	532,700
Net proceeds from offering of common stock							$ 1.4	$ 1.6
Percentage of fixed commission expense of gross proceeds of shares sold in ATM agreement					3.00%
Lincoln Park Capital Fund, LLC ("Investor")
Class of Stock
Value of shares investor has committed to purchase from time to time at Company's sole discretion			$ 35.0	$ 30.2		$ 30.2	$ 30.2
Stock issued (in shares)			269,749				600,000	785,848
Stock issued (per share)			$ 2.84
Net proceeds from offering of common stock							$ 1.1	$ 2.3
Common Stock \| "At-The-Market" Equity Program
Class of Stock
Net proceeds from offering of common stock					$ 50.0
Future plans \| Pillar Investment Entities
Class of Stock
Ownership percentage	19.99%
Pillar Investment Entities
Class of Stock
Stock issued (in shares)	3,039,514
Ownership percentage				19.99%		19.99%	19.99%
Shares of common stock that may be purchased upon exercise of warrants	3,039,514			3,039,514		3,039,514	3,039,514
Warrant exercise price (per share)	$ 2.28			$ 2.28		$ 2.28	$ 2.28
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any	$ 5.0
Combined purchase price (per share)	$ 1.645
Stock price underlying warrants (per share)	$ 0.125
Net proceeds from offering of common stock						$ 4.7
Pillar Investment Entities \| Future plans
Class of Stock
Stock issued (in shares)	2,747,252
Shares of common stock that may be purchased upon exercise of warrants	1,373,626
Warrant exercise price (per share)	$ 2.71
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any	$ 5.0
Number of common warrants	0.5
Stock price (in dollars per share)	$ 3.01
Number of consecutive trading days	20 days
Pillar Investment Entities \| Future plans \| Common stock warrants
Class of Stock
Combined purchase price (per share)	$ 1.82
Pillar Investment Entities \| Future plans \| Pre-funded Warrants
Class of Stock
Warrant exercise price (per share)	0.01
Combined purchase price (per share)	$ 1.81