Equity Financings	12 Months Ended
Dec. 31, 2017
Equity Financings
Equity Financings	Equity Financings In May 2015, the Company sold an aggregate of 8,337,500 shares of its common stock through an underwritten public offering at a price to the public of $19.00 per share. As a result of the offering, which included the full exercise of the underwriters' option to purchase additional shares, the Company received aggregate net proceeds of approximately $148.4 million, after deducting underwriting discounts and commissions and other offering expenses. In May 2014, the Company entered into an At-the-Market Equity Offering Sales Agreement, or the 2014 ATM Agreement, with Stifel, Nicolaus & Company, Incorporated, or Stifel, under which the Company was authorized to issue and sell shares of its common stock having aggregate sales proceeds of up to $75 million from time to time through Stifel, acting as sales agent and/or principal. The Company paid Stifel a commission of 2.0% of the gross proceeds from the sale of shares of its common stock under this facility. The Company concluded sales under the 2014 ATM Agreement in April 2015. In the year ended December 31, 2015, the Company sold approximately 3.8 million shares of common stock under the 2014 ATM Agreement, raising aggregate net proceeds of approximately $55.2 million. In total, the Company sold approximately 5.4 million shares of common stock, raising aggregate net proceeds of approximately $73.5 million. In April 2015, the Company entered into an ATM Agreement, or the 2015 ATM Agreement, with Stifel, under which the Company was authorized to issue and sell shares of its common stock having aggregate sales proceeds of up to $75 million from time to time through Stifel, acting as sales agent and/or principal. The Company paid Stifel a commission of 2.0% of the gross proceeds from the sale of shares of its common stock under the 2015 ATM Agreement. The Company concluded sales under the 2015 ATM Agreement in May 2017. In the year ended December 31, 2015, the Company sold approximately 0.5 million shares of common stock under the 2015 ATM Agreement, raising net proceeds of approximately $9.3 million. In the year ended December 31, 2017, the Company sold approximately 4.5 million shares of common stock pursuant to an effective shelf registration statement filed with the SEC (Reg. No. 333-209813) and a related prospectus supplement, raising net proceeds of $64.1 million, and concluded sales under the 2015 ATM Agreement.

Equity Financings

In May 2015, the Company sold an aggregate of 8,337,500 shares of its common stock through an underwritten public offering at a price to the public of $19.00 per share. As a result of the offering, which included the full exercise of the underwriters' option to purchase additional shares, the Company received aggregate net proceeds of approximately $148.4 million, after deducting underwriting discounts and commissions and other offering expenses.

In May 2014, the Company entered into an At-the-Market Equity Offering Sales Agreement, or the 2014 ATM Agreement, with Stifel, Nicolaus & Company, Incorporated, or Stifel, under which the Company was authorized to issue and sell shares of its common stock having aggregate sales proceeds of up to $75 million from time to time through Stifel, acting as sales agent and/or principal. The Company paid Stifel a commission of 2.0% of the gross proceeds from the sale of shares of its common stock under this facility. The Company concluded sales under the 2014 ATM Agreement in April 2015. In the year ended December 31, 2015, the Company sold approximately 3.8 million shares of common stock under the 2014 ATM Agreement, raising aggregate net proceeds of approximately $55.2 million. In total, the Company sold approximately 5.4 million shares of common stock, raising aggregate net proceeds of approximately $73.5 million.

In April 2015, the Company entered into an ATM Agreement, or the 2015 ATM Agreement, with Stifel, under which the Company was authorized to issue and sell shares of its common stock having aggregate sales proceeds of up to $75 million from time to time through Stifel, acting as sales agent and/or principal. The Company paid Stifel a commission of 2.0% of the gross proceeds from the sale of shares of its common stock under the 2015 ATM Agreement. The Company concluded sales under the 2015 ATM Agreement in May 2017. In the year ended December 31, 2015, the Company sold approximately 0.5 million shares of common stock under the 2015 ATM Agreement, raising net proceeds of approximately $9.3 million. In the year ended December 31, 2017, the Company sold approximately 4.5 million shares of common stock pursuant to an effective shelf registration statement filed with the SEC (Reg. No. 333-209813) and a related prospectus supplement, raising net proceeds of $64.1 million, and concluded sales under the 2015 ATM Agreement.