License and Collaboration Agreements - Additional Information (Detail) $ in Thousands, shares in Millions		1 Months Ended							12 Months Ended
	Dec. 21, 2019 USD ($) shares	Nov. 30, 2021 USD ($)	Oct. 31, 2021 USD ($)	Jul. 31, 2021 USD ($)	Nov. 30, 2019 USD ($)	Apr. 30, 2019 USD ($)	Jul. 31, 2017	Jun. 30, 2016 USD ($)	Dec. 31, 2023 USD ($) Milestone shares	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Mar. 31, 2024 USD ($)	Feb. 28, 2021 USD ($)	Dec. 31, 2019 USD ($)	Aug. 08, 2018 USD ($) shares	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Issuance costs			$ 26,500
Product revenues, net									$ 1,144,876	$ 843,769	$ 612,401
Impairment of strategic investments									30,321	2,575	4,488
Contingent consideration									38,100	36,900
Intangible asset, net									29,620	7,578
Cost of sales (excluding amortization of in-licensed rights)									150,343	139,989	97,049
Amortization of in-licensed rights									1,559	714	706
Development milestone and settlement upfront fee recognized as research and development expense									13,200	32,600	50,300
ELEVIDYS [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Product revenues, net									200,356	0
US [Member] | ELEVIDYS [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Product revenues, net									200,356	0
Minimum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of royalty payments							4.00%
Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of royalty payments							8.00%
Genethon [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expense									$ 0	0	4,000
Up-front cash payment under development					$ 157,500
Up-front cash payment under sales milestone					$ 78,800
Up-front cash payment under development percentage					75.00%
Number of development milestone | Milestone									0
Other Licensed Products [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front cash payment under development percentage					25.00%
Myonexus Therapeutics, Inc. [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Final exercise price						$ 178,300
Additional development milestone payments to be paid						$ 200,000
Contingent consideration									$ 37,700	35,500
Lacerta Therapeutics [Member] | Series A Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Impairment of strategic investments									30,000
BioMarin Pharmaceutical, Inc. [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory and sales milestone payments									0
Intangible asset, net																$ 6,600
Sales milestone payment recorded as an in-license right									0
Royalty expense									17,600	30,400	31,400
BioMarin Pharmaceutical, Inc. [Member] | AMONDYS 45 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory milestone payable													$ 10,000
BioMarin Pharmaceutical, Inc. [Member] | Intellectual Property
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amortization of in-licensed rights									2,300
BioMarin Pharmaceutical, Inc. [Member] | US [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Royalty payment expiry period		2024-03
BioMarin Pharmaceutical, Inc. [Member] | EU [member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Royalty payment expiry period		2024-12
BioMarin Pharmaceutical, Inc. [Member] | Minimum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of royalty payments		4.00%
BioMarin Pharmaceutical, Inc. [Member] | Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory and sales milestone payments		$ 50,000
Percentage of royalty payments		5.00%
BioMarin Pharmaceutical, Inc. [Member] | Maximum [Member] | Other Countries [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Royalty payment expiry period		2024-12
University of Western Australia [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory and sales milestone payments									0
Sales milestone payment recorded as an in-license right									0
Royalty expense									11,800	10,500	7,700
Carrying value of intangible assets									700
University of Western Australia [Member] | EXONDYS 51 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Sales milestone payment recorded as an in-license right																	$ 1,000
University of Western Australia [Member] | VYONDYS 53 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Sales milestone payment recorded as an in-license right														$ 500
University of Western Australia [Member] | AMONDYS 45 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Sales milestone payment recorded as an in-license right													$ 500
University of Western Australia [Member] | Maximum [Member] | EXONDYS 51 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payments to UWA on successful achievement of certain development and regulatory milestones								$ 26,000
Collaborative Arrangement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment for option exercise									165,800		0
Contingent research milestone payments									5,100	6,000	3,000
Collaborative Arrangement | Research and Development Expense [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front and development milestone expenses									7,500	8,500
Collaborative Arrangement | ELEVIDYS [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and other receivable									7,100
Collaborative Arrangement | Forecast [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and other receivable												$ 48,000
Collaborative Arrangement | Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development milestone and settlement upfront fee recognized as research and development expense									3,200
Contingent research milestone payments									$ 34,800
Collaborative Arrangement | Roche Holding A.G. [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Proceeds from license and collaborative agreement	$ 1,200,000
Issuance costs	$ 312,100
Stock issued during period shares collaboration and license agreement | shares	2.5
Payment for option exercise	$ 485,000
Single combined performance obligation	348,700
Stock options exercised or expired | shares									0.0
Product revenues, net									$ 98,500	89,200	89,500
Deferred revenue									487,400
Deferred revenue, current									50,400
Deferred revenue separate material options right									485,000	485,000
Research and development expense									106,900	117,800	90,500
Collaboration receivable									29,800	41,800
Collaborative Arrangement | Roche Holding A.G. [Member] | ELEVIDYS [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and other receivable									9,200	0
Inventory costs									1,800
Collaborative Arrangement | Roche Holding A.G. [Member] | Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory and sales milestones payment received	$ 1,700,000
Collaborative Arrangement | Genethon [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expense									6,600	$ 3,500	$ 11,700
Up-front cash payment under development					$ 28,000
Series A Preferred Stock Purchase Agreement | Lacerta Therapeutics [Member] | Series A Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front payment | shares															4.5
Series A Preferred Stock Purchase Agreement | Lacerta Therapeutics [Member] | Other Noncurrent Assets [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue															$ 30,000
License And Purchase Agreement | Lacerta Therapeutics [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue															$ 38,000
Nationwide License Agreement [Member] | ELEVIDYS [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Carrying value of intangible assets									22,200
Nationwide License Agreement [Member] | Nationwide Children's Hospital [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Sublicense payment				$ 38,000
Cost of sales (excluding amortization of in-licensed rights)									6,000
Carrying value of intangible assets									23,000
Nationwide License Agreement [Member] | Nationwide Children's Hospital [Member] | ELEVIDYS [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Carrying value of intangible assets									$ 10,000