Stockholders' Equity (Details) $ / shares in Units, $ in Thousands	1 Months Ended			12 Months Ended
	Mar. 31, 2015 USD ($) $ / shares shares	Feb. 28, 2014 USD ($) $ / shares shares	Mar. 31, 2013 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) item $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($)
Convertible Preferred Stock and Stockholders' Equity
Preferred Stock, Shares Authorized				10,000,000	10,000,000
Common Stock, Shares Authorized				100,000,000	100,000,000
Preferred Stock, Par or Stated Value Per Share | $ / shares				$ 0.0001	$ 0.0001
Common Stock, Par or Stated Value Per Share | $ / shares				$ 0.0001	$ 0.0001
Preferred Stock, Shares Issued				0	0
Preferred Stock, Shares Outstanding				0	0
Common Stock, Shares, Issued				40,279,783	36,110,082
Common Stock, Shares, Outstanding				40,279,783	36,110,082
Stock Issued During Period, Shares, New Issues	3,755,000	3,200,000	5,428,000
Shares Issued, Price Per Share | $ / shares	$ 51.00	$ 31.50	$ 18.00
Net proceeds from the sale of common stock in an underwritten public offering | $	$ 179,800	$ 94,200	$ 91,300	$ 179,753	$ 94,199	$ 91,312
Common Stock
Convertible Preferred Stock and Stockholders' Equity
Stock Issued During Period, Shares, New Issues	3,755,000	3,200,000	5,428,000
Shares Issued, Price Per Share | $ / shares	$ 51.00	$ 31.50	$ 18.00
Gross proceeds from the sale of common stock in an underwritten public offering | $	$ 191,500	$ 100,800	$ 97,700
Net proceeds from the sale of common stock in an underwritten public offering | $	$ 179,800	$ 94,200	$ 91,300
Number of votes per share | item				1