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	Sep. 30, 2014	Dec. 31, 2013
Payables and Accruals [Abstract]
Clinical and preclinical activities	$ 30,041	$ 34,182
Royalties and milestones payable	24,773	6,377
Payroll and payroll-related	19,779	23,832
Accounts payable	12,356	3,290
Accrued professional services and other current liabilities	9,405	9,379
Taxes payable	9,310
Interest payable	3,396	1,698
Total	$ 109,060	$ 78,758