Nature of Operations (Details 2) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Nature of Operation.
Net proceeds from public offering			$ 165,700,000
Gross proceeds from shares of common stock sold in an underwritten public offering			176,700,000
Net proceeds from shares of common stock sold in an underwritten public offering		$ 52,400,005	$ 18,300,000
Minimum period for which we believe that our current cash, cash equivalents, cash generated from future sales, and cash generated from the exercise of outstanding warrants will provide sufficient liquidity to fund operations	12 months