Stockholders' Equity and Convertible Preferred Stock

12 Months Ended

Dec. 31, 2017

Stockholders' Equity Note [Abstract]

Stockholders' Equity and Convertible Preferred Stock

Stockholders' Equity and Convertible Preferred Stock

Common Stock

On January 28, 2015, the Company completed an additional public offering of 4,000,000 shares of its common stock at a price of $36.75 per share, for aggregate estimated proceeds, net of underwriting discounts, commissions and offering costs, of approximately $137.8 million. Also, on January 28, 2015, the underwriters purchased an additional 600,000 shares in the aggregate by exercising an option to purchase additional shares that was granted to them in connection with the offering. As a result of the public offering and subsequent exercise of the underwriters' option, the Company received aggregate proceeds, net of underwriting discounts, commissions and offering costs of approximately $158.4 million.

On July 28, 2015, the Company completed an additional public offering of 4,054,054 shares of its common stock at a price of $74.00 per share, for aggregate proceeds, net of underwriting discounts, commissions and offering costs, of approximately $281.5 million. Also, on July 28, 2015, the underwriters purchased an additional 608,108 shares by exercising an option to purchase additional shares that was granted to them in connection with the offering. As a result of the public offering and subsequent exercise of the underwriters' option, the Company received aggregate proceeds, net of underwriting discounts, commissions and estimated offering costs of approximately $323.8 million.

Warrants

At December 31, 2017 and 2016, the company had outstanding warrants to purchase 605,415 and 630,444 shares of the Company's common stock, respectively, at prices ranging from $14.00 to $16.97 per share. The warrants became exercisable at various dates between 2011 and 2014 and expire at various dates through 2019.