Stockholders' Equity	12 Months Ended
Dec. 31, 2019
Equity [Abstract]
Stockholders' Equity	9. Stockholders’ Equity The Company’s Board of Directors has authorized 100,000,000 shares of the Company’s common stock, par value $0.001 per share, and 5,000,000 shares of undesignated preferred stock, par value $0.001 per share, that may be issued from time to time by the Board of Directors of the Company in one or more series. As of December 31, 2019, there were 46,720,225 shares of common stock and no shares of preferred stock issued and outstanding. Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are entitled to dividends when and if declared by the Board of Directors, subject to the preferential rights of the holders of preferred stock, if any. In December 2019, as a result of the achievement of a clinical performance target, restricted stock units of various executive officers vested and were converted into 36,666 shares of the Company’s common stock (see Note 13, Stock-Based Compensation). On August 20, 2019, the Company entered into a Non-Exclusive License Agreement, or the Enteris License Agreement, with Enteris Biopharma, Inc., or Enteris (see Note 17, Commitments and Contingencies for additional information regarding the Enteris License Agreement). As consideration for the licensed rights under the Enteris License Agreement, the Company paid an upfront fee equal to $8,000, consisting of $4,000 in cash and $4,000 in shares of the Company’s common stock. In connection with the Enteris License Agreement, on August 20, 2019, the Company entered into a Common Stock Purchase Agreement, or the Purchase Agreement, with Enteris and its affiliate, EBP Holdco LLC, collectively referred to as Purchaser, pursuant to which the Company issued and sold to Purchaser 170,793 shares of its common stock in a private placement in satisfaction of the $4,000 portion of the upfront fee payable in shares of the Company’s common stock pursuant to the Enteris License Agreement, and for no additional consideration, based on a purchase price of $23.42 per share, which was equal to the 30-day volume weighted average price of the Company’s common stock on August 20, 2019. In addition, if the Company exercises its right, but not obligation, to terminate its obligation to pay any royalties under the Enteris License Agreement in exchange for a lump sum payment in cash, it may elect to make 50% of the payment in stock by issuing additional shares of the Company’s common stock valued at the 30-day volume weighted average price of the Company’s common stock as of such exercise. Pursuant to its obligations under the Purchase Agreement, the Company effected the registration and sale of the shares issued and sold to Purchaser thereunder in accordance with the applicable requirements of the Securities Act of 1933, as amended, or the Securities Act, through the filing of an automatic shelf registration statement on Form S-3ASR (File No. 333-233666) with the SEC on September 9, 2019. In addition, the Purchase Agreement includes customary representations, warranties and covenants by the Company (see Note 17, Commitments and Contingencies). On July 24, 2019, the Company entered into an underwriting agreement with J.P. Morgan Securities LLC and Jefferies LLC, as representatives of the several underwriters named therein, relating to the issuance and sale by the Company of 6,325,000 shares of its common stock, which included the exercise of the underwriters’ option to purchase 825,000 additional shares of common stock, at a public offering price of $23.00 per share. The Company closed this offering on July 29, 2019, including the full exercise of the underwriters’ option to purchase 825,000 additional shares of common stock. The Company received net proceeds of $136,498, after deducting $8,977 of underwriting discounts and commissions and offering expenses. This offering was made pursuant to the Company’s Shelf Registration Statement on Form S-3 (File No. 333-230333), or the Shelf Registration Statement, filed with the SEC on March 15, 2019 and declared effective on April 4, 2019, and a related prospectus supplement dated July 24, 2019, which was filed with the SEC on July 25, 2019. The Shelf Registration Statement provides for aggregate offerings of up to $300,000 of common stock, preferred stock, debt securities, warrants or any combination thereof. The securities registered under the Shelf Registration Statement include unsold securities that had been registered under the Company’s previous shelf registration statement (File No. 333-216657) that was declared effective on March 24, 2017. In May 2019, as a result of the achievement of a clinical performance target, restricted stock units of various executive officers vested and were converted into 74,166 shares of the Company’s common stock (see Note 13, Stock-Based Compensation). On March 20, 2019, or the Effective Date, the Company entered into a consulting agreement with an existing stockholder. In accordance with the agreement, the stockholder provided various consulting services to the Company in exchange for 10,195 unregistered shares of the Company’s common stock. The closing price of the Company’s common stock on the Effective Date was $19.37 per share. The services provided by the consultant were performed during the six-month period following the Effective Date. During the year ended December 31, 2019, stock-based compensation expense of $197 was recognized in the Statements of Comprehensive Loss, all of which related to G&A expense. In December 2018, as a result of the achievement of a clinical performance target, restricted stock units of various executive officers vested and were converted into 83,791 shares of the Company’s common stock (see Note 13, Stock-Based Compensation). On July 18, 2018, the Company entered into an underwriting agreement with Jefferies LLC and Merrill Lynch, Pierce, Fenner & Smith Incorporated, as representatives of the several underwriters named therein, relating to the issuance and sale by the Company of up to 5,175,000 shares of its common stock, including 675,000 shares of common stock the underwriters had the option to purchase, at a public offering price of $19.00 per share. This offering was made pursuant to the Company’s Registration Statement on Form S‑3 (File No. 333‑216657), filed with the SEC on March 13, 2017 and declared effective on March 24, 2017, and a related prospectus dated March 24, 2017 and prospectus supplement dated July 18, 2018, which was filed with the SEC on July 20, 2018. On July 23, 2018, the Company closed the offering, including the full exercise of the underwriters’ option to purchase 675,000 additional shares of common stock. The Company received net proceeds of $92,063, after deducting $6,262 relating to underwriting discounts and commissions and offering expenses. On May 17, 2018, the Company issued 1,174,827 shares of its common stock to Vifor in connection with the license agreement entered into with VFMCRP (refer to Note 11, Collaboration and Licensing Agreements). On March 30, 2017, the Company entered into an underwriting agreement with Piper Jaffray & Co. and Stifel, Nicolaus & Company, Incorporated, as representatives of the several underwriters named therein, relating to the issuance and sale by the Company of 5,117,500 shares of its common stock, including 667,500 shares of common stock the underwriters had the option to purchase, at a public offering price of $18.00 per share, or the 2017 Offering. The 2017 Offering was made pursuant to the Company’s Registration Statement on Form S‑3 (File No. 333‑216657), filed with the SEC on March 13, 2017 and declared effective on March 24, 2017, and a related prospectus supplement dated March 30, 2017, which was filed with the SEC on March 31, 2017. On April 5, 2017, the Company closed the 2017 Offering, including the full exercise of the underwriters’ option to purchase 667,500 additional shares of common stock. The Company received net proceeds of $86,224, after deducting $5,891 relating to underwriting discounts and commissions and offering expenses.

9. Stockholders’ Equity

The Company’s Board of Directors has authorized 100,000,000 shares of the Company’s common stock, par value $0.001 per share, and 5,000,000 shares of undesignated preferred stock, par value $0.001 per share, that may be issued from time to time by the Board of Directors of the Company in one or more series. As of December 31, 2019, there were 46,720,225 shares of common stock and no shares of preferred stock issued and outstanding.

Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are entitled to dividends when and if declared by the Board of Directors, subject to the preferential rights of the holders of preferred stock, if any.

In December 2019, as a result of the achievement of a clinical performance target, restricted stock units of various executive officers vested and were converted into 36,666 shares of the Company’s common stock (see Note 13, Stock-Based Compensation).

On August 20, 2019, the Company entered into a Non-Exclusive License Agreement, or the Enteris License Agreement, with Enteris Biopharma, Inc., or Enteris (see Note 17, Commitments and Contingencies for additional information regarding the Enteris License Agreement). As consideration for the licensed rights under the Enteris License Agreement, the Company paid an upfront fee equal to $8,000, consisting of $4,000 in cash and $4,000 in shares of the Company’s common stock. In connection with the Enteris License Agreement, on August 20, 2019, the Company entered into a Common Stock Purchase Agreement, or the Purchase Agreement, with Enteris and its affiliate, EBP Holdco LLC, collectively referred to as Purchaser, pursuant to which the Company issued and sold to Purchaser 170,793 shares of its common stock in a private placement in satisfaction of the $4,000 portion of the upfront fee payable in shares of the Company’s common stock pursuant to the Enteris License Agreement, and for no additional consideration, based on a purchase price of $23.42 per share, which was equal to the 30-day volume weighted average price of the Company’s common stock on August 20, 2019. In addition, if the Company exercises its right, but not obligation, to terminate its obligation to pay any royalties under the Enteris License Agreement in exchange for a lump sum payment in cash, it may elect to make 50% of the payment in stock by issuing additional shares of the Company’s common stock valued at the 30-day volume weighted average price of the Company’s common stock as of such exercise. Pursuant to its obligations under the Purchase Agreement, the Company effected the registration and sale of the shares issued and sold to Purchaser thereunder in accordance with the applicable requirements of the Securities Act of 1933, as amended, or the Securities Act, through the filing of an automatic shelf registration statement on Form S-3ASR (File No. 333-233666) with the SEC on September 9, 2019. In addition, the Purchase Agreement includes customary representations, warranties and covenants by the Company (see Note 17, Commitments and Contingencies).

On July 24, 2019, the Company entered into an underwriting agreement with J.P. Morgan Securities LLC and Jefferies LLC, as representatives of the several underwriters named therein, relating to the issuance and sale by the Company of 6,325,000 shares of its common stock, which included the exercise of the underwriters’ option to purchase 825,000 additional shares of common stock, at a public offering price of $23.00 per share. The Company closed this offering on July 29, 2019, including the full exercise of the underwriters’ option to purchase 825,000 additional shares of common stock. The Company received net proceeds of $136,498, after deducting $8,977 of underwriting discounts and commissions and offering expenses.

This offering was made pursuant to the Company’s Shelf Registration Statement on Form S-3 (File No. 333-230333), or the Shelf Registration Statement, filed with the SEC on March 15, 2019 and declared effective on April 4, 2019, and a related prospectus supplement dated July 24, 2019, which was filed with the SEC on July 25, 2019. The Shelf Registration Statement provides for aggregate offerings of up to $300,000 of common stock, preferred stock, debt securities, warrants or any combination thereof. The securities registered under the Shelf Registration Statement include unsold securities that had been registered under the Company’s previous shelf registration statement (File No. 333-216657) that was declared effective on March 24, 2017.

In May 2019, as a result of the achievement of a clinical performance target, restricted stock units of various executive officers vested and were converted into 74,166 shares of the Company’s common stock (see Note 13, Stock-Based Compensation).

On March 20, 2019, or the Effective Date, the Company entered into a consulting agreement with an existing stockholder. In accordance with the agreement, the stockholder provided various consulting services to the Company in exchange for 10,195 unregistered shares of the Company’s common stock. The closing price of the Company’s common stock on the Effective Date was $19.37 per share. The services provided by the consultant were performed during the six-month period following the Effective Date. During the year ended December 31, 2019, stock-based compensation expense of $197 was recognized in the Statements of Comprehensive Loss, all of which related to G&A expense.

In December 2018, as a result of the achievement of a clinical performance target, restricted stock units of various executive officers vested and were converted into 83,791 shares of the Company’s common stock (see Note 13, Stock-Based Compensation).

On July 18, 2018, the Company entered into an underwriting agreement with Jefferies LLC and Merrill Lynch, Pierce, Fenner & Smith Incorporated, as representatives of the several underwriters named therein, relating to the issuance and sale by the Company of up to 5,175,000 shares of its common stock, including 675,000 shares of common stock the underwriters had the option to purchase, at a public offering price of $19.00 per share. This offering was made pursuant to the Company’s Registration Statement on Form S‑3 (File No. 333‑216657), filed with the SEC on March 13, 2017 and declared effective on March 24, 2017, and a related prospectus dated March 24, 2017 and prospectus supplement dated July 18, 2018, which was filed with the SEC on July 20, 2018.

On July 23, 2018, the Company closed the offering, including the full exercise of the underwriters’ option to purchase 675,000 additional shares of common stock. The Company received net proceeds of $92,063, after deducting $6,262 relating to underwriting discounts and commissions and offering expenses.

On May 17, 2018, the Company issued 1,174,827 shares of its common stock to Vifor in connection with the license agreement entered into with VFMCRP (refer to Note 11, Collaboration and Licensing Agreements).

On March 30, 2017, the Company entered into an underwriting agreement with Piper Jaffray & Co. and Stifel, Nicolaus & Company, Incorporated, as representatives of the several underwriters named therein, relating to the issuance and sale by the Company of 5,117,500 shares of its common stock, including 667,500 shares of common stock the underwriters had the option to purchase, at a public offering price of $18.00 per share, or the 2017 Offering. The 2017 Offering was made pursuant to the Company’s Registration Statement on Form S‑3 (File No. 333‑216657), filed with the SEC on March 13, 2017 and declared effective on March 24, 2017, and a related prospectus supplement dated March 30, 2017, which was filed with the SEC on March 31, 2017.

On April 5, 2017, the Company closed the 2017 Offering, including the full exercise of the underwriters’ option to purchase 667,500 additional shares of common stock. The Company received net proceeds of $86,224, after deducting $5,891 relating to underwriting discounts and commissions and offering expenses.