Intangible Assets, Net - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jul. 31, 2017
Finite Lived Intangible Assets [Line Items]
Amortization of in-licensed rights	$ 706,000	$ 662,000	$ 849,000
Patents [Member]
Finite Lived Intangible Assets [Line Items]
Amortization of in-licensed rights	600,000	600,000	400,000
Patents [Member] | Research and Development Expense [Member]
Finite Lived Intangible Assets [Line Items]
Book value of patent abandoned	500,000	100,000	200,000
Software Development [Member]
Finite Lived Intangible Assets [Line Items]
Amortization of in-licensed rights		$ 500,000	400,000
Maximum [Member]
Finite Lived Intangible Assets [Line Items]
Amortization of in-licensed rights			$ 800,000
Minimum [Member] | Software Development [Member]
Finite Lived Intangible Assets [Line Items]
Amortization of in-licensed rights	100,000
EXONDYS 51 [Member]
Finite Lived Intangible Assets [Line Items]
In-lincensed Rights	1,000,000.0
EXONDYS 51 [Member] | Maximum [Member] | Bio Marin [Member]
Finite Lived Intangible Assets [Line Items]
Sales milestone payment recorded as an in-license right				$ 6,600,000
VYONDYS 53 [Member]
Finite Lived Intangible Assets [Line Items]
In-lincensed Rights	500,000
VYONDYS Fifty Three [Member]
Finite Lived Intangible Assets [Line Items]
In-lincensed Rights	$ 500,000