Accounts Payable, Accrued Expenses and Other Current Liabilities - Components of Accounts Payable, Accrued Expenses and Other Current Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Accounts Payable Accrued Expenses And Other Current Liabilities [Abstract]
Clinical and preclinical activities	$ 30,318	$ 34,182
Payroll and payroll-related	13,914	23,832
Accrued professional services and other current liabilities	11,626	9,379
Royalties and milestones payable	11,352	6,377
Accounts payable	9,287	3,290
Interest payable	1,698	1,698
Total	$ 78,195	$ 78,758