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Nature of Business (Details) (USD $)
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0 Months Ended | 12 Months Ended | 0 Months Ended | |||
|---|---|---|---|---|---|---|
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Oct. 07, 2014
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Jun. 25, 2014
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Jun. 11, 2014
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Dec. 31, 2014
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Jan. 28, 2015
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Dec. 31, 2013
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| Nature of Business | ||||||
| Retained Earnings (Accumulated Deficit) | $ (344,238,000) | $ (277,301,000) | ||||
| Cash, Cash Equivalents, and Short-term Investments | 105,300,000 | |||||
| Common stock - public offering | ||||||
| Issuance of common stock (in shares) | 2,750,000 | 6,500,000 | ||||
| Proceeds from the sale of common stock | 46,900,000 | 103,804,000 | ||||
| Proceeds from public offering and exercise of underwriters option | 53,400,000 | 50,400,000 | ||||
| Common Stock | ||||||
| Common stock - public offering | ||||||
| Issuance of common stock (in shares) | 10,141,268 | |||||
| Common Stock | Subsequent Event | ||||||
| Common stock - public offering | ||||||
| Issuance of common stock (in shares) | 4,600,000 | |||||
| Shares Issued, Price Per Share | $ 36.75 | |||||
| Proceeds from the sale of common stock | 137,800,000 | |||||
| Proceeds from public offering and exercise of underwriters option | $ 158,600,000 | |||||