Stockholders' Equity (Notes)	12 Months Ended
Dec. 31, 2018
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity On June 13, 2017, the Company entered into an Underwriting Agreement, or the Underwriting Agreement, with J.P. Morgan Securities LLC and Merrill Lynch, Pierce, Fenner & Smith Incorporated acting as joint book-running managers and as representatives of the underwriters, or the Underwriters, relating to the issuance and sale of 6,382,978 shares of the Company's common stock, or the Offering. The price to the public in the Underwriting Agreement was $11.75 per share, before underwriting discounts and commissions. Under the terms of the Underwriting Agreement, the Company granted the Underwriters an option, exercisable for 30 days, to purchase up to an additional 957,446 shares of common stock pursuant to the Offering. The Offering was completed on June 19, 2017, pursuant to which the Company sold a total of 7,340,424 shares of its common stock for gross proceeds of $86,250,000. The Company incurred $5,520,000 in related transaction costs, comprising underwriting discounts and commissions of $5,175,000 paid in accordance with the Underwriting Agreement, and approximately $345,000 in additional miscellaneous offering expenses. In June 2016, the Company entered into an Equity Distribution Agreement, or the Distribution Agreement, with Canaccord Genuity Inc., as sales agent, or Canaccord, pursuant to which the Company could, at its discretion, offer and sell, from time to time, through Canaccord shares of its common stock having an aggregate offering price of up to $30,000,000. Under the Distribution Agreement, Canaccord could sell shares by any method deemed to be an “at-the-market” offering as defined in Rule 415 under the Securities Act or any other method permitted by law, including in privately negotiated transactions. The Company began sales under the Distribution Agreement in August 2016 pursuant to an effective shelf registration statement on Form S-3 previously filed with the SEC. During the three months ended September 30, 2016, the Company sold 3.3 million shares of common stock, at an average per share price of $9.04, for aggregate gross proceeds of $30,000,000. The Company incurred $1,143,000 in related transaction costs, comprising commissions paid to Canaccord of 3.0% of the aggregate gross proceeds from each sale of shares occurring pursuant to the Distribution Agreement, or $900,000, and $243,000 in additional miscellaneous expenses.

Stockholders’ Equity

On June 13, 2017, the Company entered into an Underwriting Agreement, or the Underwriting Agreement, with J.P. Morgan Securities LLC and Merrill Lynch, Pierce, Fenner & Smith Incorporated acting as joint book-running managers and as representatives of the underwriters, or the Underwriters, relating to the issuance and sale of 6,382,978 shares of the Company's common stock, or the Offering. The price to the public in the Underwriting Agreement was $11.75 per share, before underwriting discounts and commissions. Under the terms of the Underwriting Agreement, the Company granted the Underwriters an option, exercisable for 30 days, to purchase up to an additional 957,446 shares of common stock pursuant to the Offering.

The Offering was completed on June 19, 2017, pursuant to which the Company sold a total of 7,340,424 shares of its common stock for gross proceeds of $86,250,000. The Company incurred $5,520,000 in related transaction costs, comprising underwriting discounts and commissions of $5,175,000 paid in accordance with the Underwriting Agreement, and approximately $345,000 in additional miscellaneous offering expenses.

In June 2016, the Company entered into an Equity Distribution Agreement, or the Distribution Agreement, with Canaccord Genuity Inc., as sales agent, or Canaccord, pursuant to which the Company could, at its discretion, offer and sell, from time to time, through Canaccord shares of its common stock having an aggregate offering price of up to $30,000,000. Under the Distribution Agreement, Canaccord could sell shares by any method deemed to be an “at-the-market” offering as defined in Rule 415 under the Securities Act or any other method permitted by law, including in privately negotiated transactions.

The Company began sales under the Distribution Agreement in August 2016 pursuant to an effective shelf registration statement on Form S-3 previously filed with the SEC. During the three months ended September 30, 2016, the Company sold 3.3 million shares of common stock, at an average per share price of $9.04, for aggregate gross proceeds of $30,000,000. The Company incurred $1,143,000 in related transaction costs, comprising commissions paid to Canaccord of 3.0% of the aggregate gross proceeds from each sale of shares occurring pursuant to the Distribution Agreement, or $900,000, and $243,000 in additional miscellaneous expenses.