Accounts Payable, Accrued Expenses and Other Current Liabilities - Components of Accounts Payable, Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Payables And Accruals [Abstract]
Clinical and preclinical	$ 48,975	$ 31,069
Taxes payable	32,565	2,106
Payroll and payroll-related	29,215	33,272
Accounts payable	22,696	10,492
Royalties payable	20,665	13,582
Other payable to licensor	17,500	5,000
Accrued professional services and other current liabilities	14,282	8,909
Interest payable	305	1,698
Total	$ 186,203	$ 106,128