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	Dec. 31, 2014	Dec. 31, 2013
Payables and Accruals [Abstract]
Payroll and payroll-related	$ 33,272	$ 23,832
Clinical and preclinical	31,069	34,182
Royalties payable	13,582	6,377
Accounts payable	10,492	3,290
Accrued professional services and other current liabilities	8,913	6,879
Other payable to licensor	5,000	2,500
Taxes payable	2,106
Interest payable	1,698	1,698
Total	$ 106,132	$ 78,758