Accounts Payable, Accrued Expenses and Other Current Liabilities - Components of Accounts Payable, Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Clinical and preclinical	$ 39,120	$ 31,069
Payroll and payroll-related	24,372	33,272
Other payable to licensor	21,786	5,000
Royalties payable	19,850	13,582
Accounts payable	12,621	10,492
Accrued professional services and other current liabilities	10,985	8,909
Taxes payable	3,461	2,106
Interest payable	63	1,698
Total	$ 132,258	$ 106,128