Accrued expenses and other current liabilities - Summary of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Payables And Accruals [Abstract]
Accrued goods and services	$ 38,067	$ 29,533
Employee compensation	10,242	19,657
Accrued license and milestone fees	10,173	4,584
Accrued professional fees	1,599	1,402
Financing lease obligation, current portion	1,048	1,051
Other	559	838
Total accrued expenses and other current liabilities	$ 61,688	$ 57,065