Leases - Additional Information (Detail) $ in Thousands			1 Months Ended
	Jul. 02, 2025 ft²	Feb. 18, 2025 USD ($) ft² $ / ft² Lease	Feb. 28, 2022 ft²	Jan. 31, 2026 USD ($)	Jun. 30, 2025 USD ($)	Apr. 30, 2025 USD ($)	Feb. 28, 2025 USD ($)	Dec. 31, 2024 USD ($)
Lessee Lease Description [Line Items]
Lease payments					$ 124,132
Lease liability					102,591
Operating lease right-of-use assets					129,045			$ 219,292
Prepaid Rent					36,829			$ 0
Undiscounted future operating lease payments					21,541
Winter Street Lease [Member]
Lessee Lease Description [Line Items]
Area of space leased | ft²			140,000
Operating lease, description			In February 2022 and subsequently amended in June 2023, the Company entered into an agreement to lease approximately 140,000 square feet of office, general laboratory and manufacturing space at 840 Winter Street in Waltham
Operating lease, modification payments		$ 78,000				$ 30,000	$ 34,000
Number of lease components | Lease		2
Lease payments		$ 52,100
Incremental borrowing rate		6.60%
Reduced in the lease liability		$ 61,900
Modified lease liability					46,500
Modified right of use asset					50,000
Lease liability					16,400
Operating lease right-of-use assets					44,700
Winter Street Lease [Member] | Forecast [Member]
Lessee Lease Description [Line Items]
Operating lease, modification payments				$ 14,000
Tech Square Lease [Member]
Lessee Lease Description [Line Items]
Area of space leased | ft²		101,000
Area of space leased expandable | ft²		46,000
Lessee operating lease delivery date		Jul. 01, 2025
Operating lease rent per square foot | $ / ft²		108
Operating lease, renewal term		5 years
Operating lease percentage of annual increase		3.00%
Improvement allowances received		$ 1,000
Lease payments		$ 192,300
Prepaid Rent					6,800
Operating lease, existence of option to extend		true
Operating lease, options to extend		Company has an option to extend the Tech Square Lease for an additional term of five years
Operating lease, option to extend		In addition, the Tech Square Lease would expand, in two tranches, to include approximately 46,000 square feet of additional office and laboratory space at 400 Tech Square (the “Additional Tech Square Premises”) when each such space becomes available.
Undiscounted future operating lease payments					156,800
Tech Square Lease [Member] | Maximum [Member]
Lessee Lease Description [Line Items]
Operating lease, term of contract		12 years
Tech Square Lease [Member] | Minimum [Member]
Lessee Lease Description [Line Items]
Operating lease, term of contract		3 months
Tech Square Lease [Member] | Subsequent Event [Member]
Lessee Lease Description [Line Items]
Area of space leased | ft²	124,000
Area of space leased expandable | ft²	23,000
Tech Square Lease Amendment [Member]
Lessee Lease Description [Line Items]
Undiscounted future operating lease payments					$ 36,900
Additional Tech Square Premises [Member] | Subsequent Event [Member]
Lessee Lease Description [Line Items]
Area of space leased expandable | ft²	23,000
Winter Street and Tech Square Lease [Member]
Lessee Lease Description [Line Items]
Total consideration		$ 244,400