License and Collaboration Agreements - Additional Information (Detail) $ in Thousands, shares in Millions			1 Months Ended					3 Months Ended	12 Months Ended
	Nov. 25, 2024 USD ($)	Dec. 21, 2019 USD ($) shares	Nov. 30, 2021 USD ($)	Nov. 30, 2019 USD ($)	Apr. 30, 2019 USD ($)	Jul. 31, 2017	Jun. 30, 2016 USD ($)	Mar. 31, 2025 USD ($)	Dec. 31, 2024 USD ($) Milestone	Dec. 31, 2023 USD ($) Milestone	Dec. 31, 2022 USD ($) Milestone	Feb. 28, 2021 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and other									$ 114,019	$ 98,460	$ 89,244
Product revenues, net									1,787,960	1,144,876	843,769
Impairment of strategic investments									0	30,321	2,575
Contingent consideration									47,400	38,100
Intangible asset, net									26,887	29,620
Cost of sales (excluding amortization of in-licensed rights)									319,099	150,343	139,989
Amortization of in-licensed rights									2,405	1,559	714
Development milestone and settlement upfront fee recognized as research and development expense										13,200	32,600
ELEVIDYS [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Product revenues, net									820,791	200,356	0
US [Member] | ELEVIDYS [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Product revenues, net									820,791	200,356	0
Forecast [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and other								$ 112,000
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%
Roche Holding A.G. [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expense									$ 127,100	$ 106,900	$ 117,800
Genethon [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of development milestone | Milestone									0	0	0
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									$ 47,100	$ 37,700
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	0	$ 0
Intangible asset, net														$ 6,600
Sales milestone payment recorded as an in-license right									0	0	0
Royalty expense									4,400	17,600	30,400
BioMarin Pharmaceutical, Inc. [Member] | Intellectual Property
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amortization of in-licensed rights									1,800
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%
University of Western Australia [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory and sales milestone payments									0	0	0
Sales milestone payment recorded as an in-license right									0	0	0
Royalty expense									12,100	11,800	10,500
Carrying value of intangible assets									500
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]
Upfront Fee To Be Paid On Certain Achievement							$ 26,000
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									116,800
Collaboration and other										89,200	89,200
Product revenues, net									48,000
Contingent research milestone payments									0	5,100	6,000
Collaborative Arrangement | Research and Development Expense [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front and development milestone expenses									0	7,500	8,500
Collaborative Arrangement | Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development milestone and settlement upfront fee recognized as research and development expense									2,300,000
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
Product revenues, net									114,000	98,500	89,200
Deferred revenue									455,300	487,400
Deferred revenue, current									130,300	50,400
Collaboration receivable									34,600	29,800
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									6,800	6,600	$ 3,500
Up-front cash payment under development				$ 28,000
Licensing and Collaboration Agreement [Member] | Arrowhead Pharmaceuticals Inc [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total Collaboration Agreement Fee	$ 250,000
Term of installment fee	five years
Annual installment fee	$ 50,000
Upfront Fee To Be Paid On Certain Enrollment Achievement	300,000
Up front payment for license and collaboration agreement	500,000
Investment in license agreement	325,000
Development milestone and settlement upfront fee recognized as research and development expense	$ 10,300,000
Licensing and Collaboration Agreement [Member] | Arrowhead Pharmaceuticals Inc [Member] | Minimum [Member] | Subsequent Event [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expense								500,000
Licensing and Collaboration Agreement [Member] | Arrowhead Pharmaceuticals Inc [Member] | Maximum [Member] | Subsequent Event [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expense								$ 600,000
Nationwide License Agreement [Member] | ELEVIDYS [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Carrying value of intangible assets									20,600
Nationwide License Agreement [Member] | Nationwide Children's Hospital [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Cost of sales (excluding amortization of in-licensed rights)									$ 30,600	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