Summary of Other (Loss) Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Nonoperating Income Expense [Abstract]
Interest expense									$ (30,669)	$ (33,709)	$ (5,801)
Interest income									7,238	6,810	1,809
Amortization of investment discount									15,350	8,573	1,401
Other expense									(236)	(656)	601
Gain from sale of Priority Review Voucher											125,000
Total other (loss) income	$ (4,773)	$ (2,510)	$ (862)	$ (172)	$ (2,311)	$ (6,968)	$ (5,218)	$ (4,485)	$ (8,317)	$ (18,982)	$ 123,010