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	Mar. 31, 2014	Dec. 31, 2013
Accounts Payable Accrued Expenses And Other Current Liabilities [Abstract]
Clinical and preclinical studies	$ 39,807	$ 34,182
Royalties and milestones payable	8,188	6,377
Accounts payable	9,388	3,290
Payroll and payroll-related	8,924	23,832
Accrued professional services and other current liabilities	8,451	9,379
Interest payable	3,396	1,698
Total	$ 78,154	$ 78,758