Summary of Other(Loss) Income (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Nonoperating Income Expense [Abstract]
Interest expense	$ (13,713)	$ (7,426)	$ (27,328)	$ (14,761)
Interest income	638	2,104	2,777	4,465
Amortization of investment discount	999	4,581	3,963	8,913
Gain from sale of Priority Review Voucher			108,069
Other (expense) income	(371)	(121)	721	349
Total other (loss) income	$ (12,447)	$ (862)	$ 88,202	$ (1,034)