Stockholders’ Equity	3 Months Ended
Mar. 31, 2020
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Preferred Stock As of March 31, 2020 and December 31, 2019, there were 2,000,000 shares of preferred stock, $0.0001 par value per share, authorized and no shares of preferred stock issued or outstanding. Common Stock As of March 31, 2020 and December 31, 2019, there were 170,000,000 shares of common stock, $0.0001 par value per share, authorized and 69,049,102 and 65,378,890 shares issued and outstanding, respectively. Controlled Equity Offering (or "At the Market" Offering) On March 22, 2019, the Company entered into a sales agreement (the “Sales Agreement”) with Cantor Fitzgerald & Co. (the “Agent”), pursuant to which the Company may offer and sell from time to time shares of the Company’s common stock through the Agent. The offering and sale of up to $40.0 million of the shares has been registered under the Securities Act of 1933, as amended (the "Securities Act"), pursuant to the Company’s registration statement on Form S-3 (File No. 333-227363), which was originally filed with the SEC on September 14, 2018 and declared effective by the SEC on October 1, 2018, the base prospectus contained within the registration statement, and a prospectus supplement that was filed with the SEC on March 22, 2019. Sales of the shares, if any, pursuant to the Sales Agreement, may be made in sales deemed to be an “at the market" offering as defined in Rule 415(a) of the Securities Act, including sales made directly through the Nasdaq Global Market or on any other existing trading market for the Company’s common stock. The Company intends to use the proceeds from the offering for working capital and other general corporate purposes. The Company may suspend or terminate the Sales Agreement at any time. During the year ended December 31, 2019, the Company sold 1,840,443 of shares of its common stock pursuant to the Sales Agreement for gross proceeds of $5,383,079, at a weighted average selling price of approximately $2.92. The Company paid $309,479 in commissions and offering fees related to the sale of the common stock. As of March 31, 2020, approximately $34,616,921 remains available for sale under this facility. We are not required to sell any shares at any time during the term of the facility. Our ability to sell common stock under the facility may be limited by several factors including, among other things, the trading volume of our common stock and certain black-out periods that we may impose upon the facility, among other things. Public Offering of Common Stock On February 4, 2020, the Company entered into an underwriting agreement with Cantor Fitzgerald & Co., as underwriter, pursuant to which the Company agreed to issue and sell an aggregate of up to 3,670,212 shares of its common stock, which included 478,723 optional shares that may be sold pursuant to an over-allotment option granted to the underwriters. On February 6, 2020, the Company closed the sale of 3,191,489 shares of its common stock at the public offering price of $2.22 per share (the "Offering"). On February 19, 2020, the underwriter exercised its over-allotment option to purchase an additional 478,723 shares at a price of $2.22 per share, which closed on February 21, 2020. The Company raised a total of $8.0 million, net of an estimated issuance costs of $0.1 million, relating to the sale of the common stock in the Offering. The Offering was made pursuant to the Company’s effective Registration Statement on Form S-3 (File No. 333-227363), which was previously filed with the SEC.

Stockholders’ Equity

Preferred Stock

As of March 31, 2020 and December 31, 2019, there were 2,000,000 shares of preferred stock, $0.0001 par value per share, authorized and no shares of preferred stock issued or outstanding.

Common Stock

As of March 31, 2020 and December 31, 2019, there were 170,000,000 shares of common stock, $0.0001 par value per share, authorized and 69,049,102 and 65,378,890 shares issued and outstanding, respectively.

Controlled Equity Offering (or "At the Market" Offering)

On March 22, 2019, the Company entered into a sales agreement (the “Sales Agreement”) with Cantor Fitzgerald & Co. (the “Agent”), pursuant to which the Company may offer and sell from time to time shares of the Company’s common stock through the Agent. The offering and sale of up to $40.0 million of the shares has been registered under the Securities Act of 1933, as amended (the "Securities Act"), pursuant to the Company’s registration statement on Form S-3 (File No. 333-227363), which was originally filed with the SEC on September 14, 2018 and declared effective by the SEC on October 1, 2018, the base prospectus contained within the registration statement, and a prospectus supplement that was filed with the SEC on March 22, 2019.

Sales of the shares, if any, pursuant to the Sales Agreement, may be made in sales deemed to be an “at the market" offering as defined in Rule 415(a) of the Securities Act, including sales made directly through the Nasdaq Global Market or on any other existing trading market for the Company’s common stock. The Company intends to use the proceeds from the offering for working capital and other general corporate purposes. The Company may suspend or terminate the Sales Agreement at any time.

During the year ended December 31, 2019, the Company sold 1,840,443 of shares of its common stock pursuant to the Sales Agreement for gross proceeds of $5,383,079, at a weighted average selling price of approximately $2.92. The Company paid $309,479 in commissions and offering fees related to the sale of the common stock. As of March 31, 2020, approximately $34,616,921 remains available for sale under this facility.

We are not required to sell any shares at any time during the term of the facility. Our ability to sell common stock under the facility may be limited by several factors including, among other things, the trading volume of our common stock and certain black-out periods that we may impose upon the facility, among other things.

Public Offering of Common Stock

On February 4, 2020, the Company entered into an underwriting agreement with Cantor Fitzgerald & Co., as underwriter, pursuant to which the Company agreed to issue and sell an aggregate of up to 3,670,212 shares of its common stock, which included 478,723 optional shares that may be sold pursuant to an over-allotment option granted to the underwriters. On February 6, 2020, the Company closed the sale of 3,191,489 shares of its common stock at the public offering price of $2.22 per share (the "Offering").

On February 19, 2020, the underwriter exercised its over-allotment option to purchase an additional 478,723 shares at a price of $2.22 per share, which closed on February 21, 2020. The Company raised a total of $8.0 million, net of an estimated issuance costs of $0.1 million, relating to the sale of the common stock in the Offering. The Offering was made pursuant to the Company’s effective Registration Statement on Form S-3 (File No. 333-227363), which was previously filed with the SEC.