Condensed Consolidated Statements of Operations and Comprehensive Loss (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Expenses:
Research and development	$ 33,545	$ 28,117
General and administrative	11,242us-gaap_GeneralAndAdministrativeExpense	4,688us-gaap_GeneralAndAdministrativeExpense
Acquired in-process research and development		17,000
Total expenses	44,787us-gaap_OperatingExpenses	49,805us-gaap_OperatingExpenses
Loss from operations	(44,787)us-gaap_OperatingIncomeLoss	(49,805)us-gaap_OperatingIncomeLoss
Interest expense	(3,726)us-gaap_InterestExpenseBorrowings
Interest income	7us-gaap_InvestmentIncomeInterest	5us-gaap_InvestmentIncomeInterest
Net loss	(48,506)	(49,800)
Net loss per share applicable to common stockholders - basic and diluted (in dollars per share)	$ (1.30)us-gaap_EarningsPerShareBasicAndDiluted	$ (1.43)us-gaap_EarningsPerShareBasicAndDiluted
Weighted-average number of common shares used in net loss per share applicable to common stockholders - basic and diluted (in shares)	37,312	34,856
Comprehensive loss	$ (48,506)us-gaap_ComprehensiveIncomeNetOfTax	$ (49,800)us-gaap_ComprehensiveIncomeNetOfTax

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Aggregate amount of interest expense on all borrowings.

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Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

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Generally recurring costs associated with normal operations except for the portion of these expenses which can be clearly related to production and included in cost of sales or services. Includes selling, general and administrative expense.

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The amount of the write-off for research and development assets that were acquired in a transaction other than a business combination.

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The costs incurred in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, excluding in-process research and development acquired in a business combination consummated during the period. Excludes software research and development, which has a separate concept.

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Average number of shares or units issued and outstanding that are used in calculating basic and diluted earnings per share (EPS).

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