Summary of Other Current Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Prepaid Expense And Other Assets Current [Abstract]
Manufacturing-related deposits and prepaids	$ 47,795	$ 39,036
Prepaid clinical and pre-clinical expenses	9,062	9,706
Prepaid research expenses	3,957	1,932
Prepaid insurance	3,699	1,006
Leasehold improvement receivable	3,059	13,474
Prepaid maintenance services	2,794	2,994
Prepaid income tax	2,132	2,130
Prepaid commercial expenses	1,408	1,573
Other	5,109	5,931
Total other current assets	$ 79,015	$ 77,782