Accounts Payable, Accrued Expenses and Other Current Liabilities - Components of Accounts Payable, Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Clinical and preclinical	$ 35,676	$ 31,069
Accrued professional services and other current liabilities	17,117	8,909
Payroll and payroll-related	19,285	33,272
Royalties payable	18,860	13,582
Accounts payable	12,754	10,492
Other payable to licensor	14,057	5,000
Interest payable	1,101	1,698
Taxes payable		2,106
Total	$ 118,850	$ 106,128