Commitments and Contingencies - Summary of Aggregate Non-Cancelable Contractual Obligations Arising from Manufacturing Obligations (Detail) $ in Thousands	Sep. 30, 2026 USD ($)
Commitments And Contingencies [Line Items]
2026 (October-December)	$ 168,990	[1]
2027	145,452	[1]
2028	39,640	[1]
Total manufacturing commitments	$ 354,082	[2]

[1] Total manufacturing commitments include obligations related to the global supply of ELEVIDYS, including inventories necessary to supply Roche for sales of ELEVIDYS in territories outside of the U.S. where Roche has received certain approvals for ELEVIDYS.

[2] Total manufacturing commitments include the Catalent Agreement (defined below), to which the Company has right of use assets and lease liabilities recorded on the unaudited condensed consolidated balance sheets as of September 30, 2026. For more information, please read Note 23, Commitments and Contingencies to the financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2025.